情态是语言学研究的一个重要语法范畴。语言中表达情态的方式有很多，其中一种重要的手段就是情态动词。汉语非常突出地使用情态动词表达情态。较之中古汉语，近代汉语的情态动词系统发生了很大的改变，一些旧的情态动词没落了，一些新的情态动词产生了，但目前学界还没有对近代汉语情态动词形成、演变进行过较为系统的研究，鉴于此，本文选择了这一研究课题对近代汉语的情态动词进行专题研究。本文综合考虑时代性、地域性、同质性等条件，选出150多部近代汉语文献构建了多语体、多体裁的平衡语料库，以近代汉语时期新兴的四组情态动词“定”、“准”、“许”、“该”作为研究对象，对四组情态动词在唐至清末各阶段的使用频度进行了量化统计。在此基础上，借鉴西方语法化理论和构式化理论，描写了四组情态动词分别由形容词（定、准）或一般动词（准、许、该）语法化为情态动词的过程、路径，阐释了演变的条件、机制，以及与这四组词相关的双音形式等。本研究将词义演变视为一个连续化环境，对非典型环境的萌发态、临界环境的歧解态和孤立环境的习用态进行了细致分析。研究发现近代汉语这四组情态动词都可以表达两种以上的情态类型，具有多义性；导致其形成和演变的条件有的来自语言外部，有的来自语言内部。这四组情态动词语法化路径为：动词“准”、“许”的演变路径：[允让]——道义许可——认识可能。“准”和“许”经常用于上下级语境（如诏、敕等下行文中），上级的权威性构成外部道义源；句法上，施事论元经常性省略，其他论元向话题位置前移，引发重新分析。动词“该”的演变路径：[对应/符合]——道义盖然——认识盖然。动词“该”经常用于礼法语境，法令的强制性构成外部道义源；语言内部条件为法令名词经常性省略，“该”直接置于动词前，触发演变机制。形容词“定”和“准”的演变路径：[确定]——认识必然——动力意愿——道义必然。形容词“定”和“准”句法组合对象由名词扩展至动词，引发重新分析。与类型学语义地图比较，这条由认识情态向根情态发展的路径比较特殊。此外，句子结构内部的前后成分也是直接影响这四组情态动词演变的因素。如主语的人称，情态动词后接动词的动态与静态之差异、否定与肯定修饰之差异等等，但不同的词对各项条件的敏感度有所不同，体现出语言演变的复杂性。

Modality is an important grammatical category in languages. There are many ways to express modality, and modal verbs are generally used in Chinese. However, there have not been any modern Chinese’s modal verb form and any systematic study on the evolution of their system yet. A huge alteration in the system of the modern Chinese’s modal verb was found when the study compared it with the ancient Chinese’s. Some ancient Chinese’s modal verbs （such as, “He(合)”,“Rong(容)”, “Bi(必)”, “Yi(宜)” and so forth）have been missing, while some modal verbs （such as, “Ding(定)”, “Zhun(准)”, “Xu(许)”, “Gai(该)” and so forth）were originated in modern Chinese time-period.Time period, regional, homogeneity and other conditions, are considered, in order to selecting more than 150 parts of the modern Chinese literature and building multi language style - multi language genre of a balanced corpus. The four sets of modal verbs during Modern Chinese time-period, which are “Ding(定)”, “Zhun(准)”, “Xu(许)”, “Gai(该)”, are studied as the research objects. The usage frequency from Tang dynasty until the end of Qing dynasty of these four modal verbs were collected. Based on this research procedure, the Western grammaticalization theory and its construction theory, the four sets of modal verbs are described by their process and path through the grammaticalization of adjectives (“Ding(定)”, “Zhun(准)”) or the grammaticalization of general verbs (“Zhun(准)”, “Xu(许)”, “Gai(该)”), respectively. The evolution of the conditions, mechanisms, and the relationship with two-tone form and so on were interpreted, as well.In this study, the evolution of lexical meaning is regarded as a continuous environment, and the conventional state of isolating context are analyzed in detail. The four groups of modal verbs in modern Chinese can express more than two types of modality (epistemic modality, moral modality and dynamic modality), this leads to uncertainty; The formation and evolution could be coming from both of outside and inside circumstance of the language. These four groups of modal verbs generally have three paths:The evolution path of verbs “Zhun(准)” and “Xu(许)”: [permit(允让)]——can(道义许可)——maybe(认识可能). They were often used in both upper and lower level context (such as, imperial edict, song and so forth), the high authoritative constituted the external source of morality; agentive argument often syntactically omitted, while other argument were moved toward to subject position, and this triggered a re-analysis.The evolution path of verb “Gai(该)”: [correspond with(对应)]——should(道义盖然)——should be(认识盖然). “Gai(该)” often used in etiquette context, statutory mandatory external moral sources; Language internal conditions is frequently omitted for the legal term, “Gai(该)” is placed directly before the verb, and this initiated mechanism of evolution.The evolution path of adjectives“Ding(定)”and “Zhun(准)”: [certain(确定)]——must be(认识必然)——must(动力意愿)——have to(道义必然). Their syntactic combination object is extended from noun to verb, which causes a new analysis. When the study compared them with types in semantic maps, the path of the development of the modal to the root is more special. The path from epistemic modality to the source of modality development is are uniquely.Besides, Front-side and backside of the sentence structure also have an effect on the evolution of these modal verbs; such as the subject person (the first / second / third), the differences between dynamic and static of the verbs after the modal verbs, the differences between negative and positive modification and so on. Nevertheless, Condition sensitivity of “Ding(定)”, “Zhun(准)”, “Xu(许)”, “Gai(该)” are different from each other, which reflects the complexity of language evolution.