本课题开创性地从移民盈余这一总体福利效应视角系统探究中国国内范围的移民是否增进以及如何增进城市本地劳动者福利。首先，构建异质劳动力移民模型和一般均衡分析框架解析移民盈余的形成机制并求解移民盈余的识别方程；然后，基于微观数据对不同情形下不同类型的城市移民盈余进行多维测度与结构分析，并通过构建中介效应模型实证辨析城市移民盈余形成的主要驱动因素；最后，基于反事实模拟方法和情景分析法进一步考察渐进放松移民限制后的城市移民盈余变化，从而确定城市移民盈余优化的最优政策选择。本研究致力于揭示城市移民与本地劳动者之间互惠共赢的共生性关系及其背后的逻辑机制，以期为中国当前城市人口与就业政策优化以及探索促进城市或城市群高质量就业的劳动力优化配置政策提供指导。

From the perspective of the overall welfare effect of migration surplus, this paper systematically studies the domestic migration whether and how to improve the welfare of urban local workers in China. Firstly, a heterogeneous labor force migration model and a general equilibrium analysis framework are constructed to analyze the formation mechanism of migration surplus and to solve the identification equation of migration surplus. Secondly, based on the micro-data, this project carries on the multi-dimensional measure and the structure analysis to the different types of urban migration surplus, and empirically tests the main driving factors of urban migration surplus with mediating effect model. Finally, based on the anti-fact simulation method and scenario analysis method, it further investigates the change of urban migration surplus after gradual easing of immigration restrictions, so as to determine the optimal policy choice for the optimization of urban migration surplus. On the one hand, this study aims to reveal the mutually beneficial symbiosis between urban migrants and local workers and the logical mechanism behind it. On the other hand, it is expected to provide guidance for the optimization of current urban population and employment policies in China and the exploration of optimal allocation policies for promoting high-quality employment in cities or urban clusters.