CISG是迄今为止最为重要且最为成功的国际统一实体私法条约，公约有多个条款提及“惯例”，其具有合同解释、空白填补等重要作用，在国际实践中有众多相关案例。然而，自CISG于1988年1月1日对中国生效后，国内法院却极少适用CISG中的惯例条款。笔者认为主要原因是CISG中的惯例条款过于简单模糊，且在新的时代背景下商事交易的形式已发生了巨大变化。因此，笔者认为需探讨CISG中的惯例在当今商事环境中的适用条件。首先，本文细致分析了惯例的起源、传统逻辑和商事交易背景的变化。惯例起源于中世纪，传统假设认为最初无统一私法可以规范跨境贸易时，惯例这一自治规则内容确定清晰并节省交易成本，反映了商人之间的最佳做法而被众所周知并经常遵守。然而，20世纪以来科技进步影响了商事交易，标准合同开始主导交易方式，商事惯例的传统逻辑逐渐难以适应不断变化的商业活动，甚至可能会对交易效率产生负面影响。因此，对惯例适用条件的分析需要以当今国际交易现实和商人需求为基础。其次，本文通过逻辑推理和现实考量，分析出了惯例适用的理论要件和实践情况。CISG所规定的两种可以直接约束当事人的惯例，理论上需要符合主客观条件。其一，当事人所同意的惯例，客观上是指普遍意义上的所有成文、不成文惯例；主观上要符合当事人明示或默示同意。其二，视为当事人所同意的惯例，客观上是指被特定贸易同类合同的当事人广泛知晓并经常遵守，主观上是指当事人“理应知道”或“非所应知但已实际知道”。主客观条件均满足，且双方并未协议排除适用惯例时，该惯例便被拟制为CISG第9条第1款的“默示同意”，从而对双方产生约束力。然而，实践中某种贸易惯例是否可以对国际货物买卖合同当事人产生约束力，最终是一个证据问题，双方的对抗最终表现为证据的对抗。最后，本文对CISG中的其他惯例条款进行了分析解读。CISG第4条和第9条分别使用了惯例的“效力”和“约束力”两种表述，本文认为惯例的约束力相当于合同成立后的约束力，惯例的效力相当于已成立合同经过国内法律评价后产生的效力。通过以上研究结果，本文希望可以赋予惯例以更清晰、确定的适用要件，以促进惯例适用和跨境商事交易。

The CISG is by far the most important and successful international unified substantive private law treaty, and has had a profound impact on national legislation and the uniform private law treaties. There are several articles in the Convention referring to “usage”, playing an important role in contract interpretation and gap-filling, and there are many relevant cases in international practice. However, since the CISG entered into force for China, the relevant article in the CISG have rarely been applied by domestic courts. The main reasons are considered to be that the usage articles in CISG are too simple and vague, and that the form of commercial transactions has changed dramatically in the new era. Therefore, in order to properly understand and apply the usage articles in the CISG, it is necessary to explore the conditions of application of the usages in the CISG in today‘s commercial environment from the historical evolution of the usages, as well as from the contextual and systemic interpretation.Firstly, this master thesis meticulously analyzes the origins and traditional logic of usages, as well as the changing context of commercial transactions. Usages has its roots in the Middle Ages, and the traditional assumption is that when there was no uniform private law to govern cross-border trade, usages, an autonomous rule that was clear and identifiable and saved transaction costs, reflected the best practices among merchants and was well known and often observed. However, as technological advances have affected commercial transactions since the 20th century, and standard contracts have begun to dominate the way transactions are conducted, the traditional logic of commercial usages has gradually become difficult to adapt to changing business activities, and may even have a negative impact on the efficiency of transactions. Therefore, the analysis of the conditions of application of the usages needs to be based on the reality of today‘s international transactions and the needs of businessmen.Secondly, through logical reasoning and practical considerations, this thesis analyzes the theoretical elements and practical situations for the application of usages. Two kinds of usages stipulated by the CISG can directly bind the parties, which theoretically need to meet the subjective and objective conditions. One, any usage to which the parties have agreed, objectively refers to the universal sense of all written and unwritten practice; subjectively to meet the parties express or implied consent. Secondly, the usages considered to be agreed by the parties means objectively that it is widely known to, and regularly observed by, parties to contracts of the type involved in the particular trade concerned, and subjectively that the parties“ought to have known”or“ought not to have known but actually knew”. The objective and subjective elements are judged in sequence, and the objective elements are met before the subjective elements are judged. When the objective and subjective conditions are met, and the parties have not agreed to exclude the application of the usages, the usages then becomes binding on both parties. However, whether a certain trade usage can bind the parties to an international contract for the sale of goods in practice is ultimately a matter of evidence, and the confrontation between the parties ultimately manifests itself as a confrontation of evidence, which must be dealt with on a case-by-case basis because the circumstances of obtaining evidence vary from case to case, which also means that the final outcome is difficult to predict. Finally, this thesis analyzes and interprets other usages articles in the CISG. Article 4 and Article 9 of the CISG use the expressions “validity” and “binding effect” of the usages respectively. This thesis believes that the binding effect of the usages is equivalent to the binding effect after the formation of the contract, and the validity of the usages is equivalent to the effect of a contract that has been evaluated by domestic law.Through the above findings, this thesis hopes that usages can be given clearer and more definite elements of application to facilitate the application of usages and cross-border commercial transactions.