论文从梳理北京老城历史文化街区面临的复杂困境入手，以街区碎化、邻里碎化与院落碎化阐释不同空间层次中的社会与空间问题，归纳其基本特征和动力机制，以空间层次多维性、社会-空间二重性和螺旋向下持续性三个特征揭示历史文化街区面临的核心困境。从价值共识、政策体系、空间行动和管控治理等四个方面入手，论述保护实践的成效与局限，揭示保护实践中存在的认知、实施和逻辑本质，提出“多层次共同体”目标下的整体性策略，并以若干地区的经验总结和规划构想作为实证支撑。 第一部分以“深度碎化”为主线，通过对北京老城演进回顾和历史文化街区的实证案例、数据调查和空间分析，剖析不同空间层次中社会与空间问题交叠嵌套并且自我螺旋向下衰败的本质，以不同层次的结构极化与空间马赛克状况，揭示了深度碎化对历史文化街区保护产生的深刻影响。 第二部分以“整合失效”为主线，总结评价历史文化街区保护实践中人口与住房政策、不同类型空间行动、公共管控与居民参与的成效与局限，以规则、空间与管治界线的模糊与收缩来解释保护实践失效的逻辑本质。 第三部分以“有效重整”为主线，提出构建多层次的社会-空间共同体是历史文化街区保护的整体性目标，对价值共识、政策体系、空间行动和管控治理提出整体性策略，并以实践案例和规划设想为例，探索有效重整的具体路径。论文将空间分异与空间生产理论拓展至微观视角，拓展空间与社会的双向动力机制研究，以深度碎化揭示历史文化街区保护困境的本质，评价保护实践的得失，剖析保护实施机制的逻辑局限，以有效重整明晰保护实践的整体性策略与保护实施机制优化的适宜途径。

This dissertation starts from arranging the complicated dilemma that the Historic Areas in Beijing is confronting. The social-spatial issues in different hierarchies of spaces are illustrated with the ideas of Characteristic Area Fragmentation, Courtyard Fragmentation as well as Household-Door Fragmentation, summarizing the fundamental characteristics and driving forces. The essence of the Beijing Historic Areas dilemma is revealed by three features --the “Deep Fragmentation” of spatial hierarchies’ multi-dimensionality, the social-spatial duality and the continuity of downward spiral. From four aspects of the conservation implementation, which are the consensus on values, the political system, the spatial behavior and the regulative governance, the gain and loss of the conservation practice is demonstrated. “Failure of Integration” and “Demarcation Behavior” indicates the misunderstandings, inadequate implementations and logic flaws in conservation practice. Approaches and holistic strategies of optimizing the conservation implementation system are put forward in order to achieve the goal of multi-hierarchy community. The first part of the paper focuses on “Deep Fragmentation”. Through reviewing the evolution of the Beijing old city as well as case studies, statistic investigations and spatial researches of Historic Areas, analyses on the dilemma are conducted, where social-spatial problems overlap and spiral down within Characteristic Area Fragmentation, Courtyard Fragmentation and Household-Door Fragmentation. Based on the polarization of structures on different hierarchies and the mosaic distribution of space, the deep impacts on Historical Areas that “Deep Fragmentation” brings about are stated. “Failure of Integration” is the key topic in the second part of this dissertation, which concentrates on the prominent problems on foundation of consensus, housing issues, featured environments, facilities and supplies as well as co-governance. It systematically summarized the deficiencies in the conservation implementation of the Historic Areas. The logical essence of the conservation failure is explained by the shrinkage and ambiguity of “Boundaries” as well as the singularity of objective. In the third part, “Effective Reintegration” is discussed, which demonstrates that constructing multi-hierarchies’ social-spatial community should be the overall objective of conservation of the Historic Areas. Upon this objective and the past experiences, holistic strategies are proposed on the consensus on values, the political system, the spatial behavior and the regulative governance. Meanwhile, specific methods on “Effective Reintegration” are explored based on examples of practical cases and planning proposals. In general, “Deep Fragmentation” reveals the essence of conservation dilemma; “Failure of Integration” introspects the gain and loss of conservation practice; “Demarcation Behavior” analyzes the logical defects in conservation implementation system and “Effective Reintegration” indicates the overall objectives in conservation practice as well as the appropriate approaches on optimizing the conservation implementation system.