This paper examines the factors associated with return migration using data from a sur- vey on rural labour transfer and urbanization in seven provinces in central-west China. Rural return migration is influenced，on the one hand，by employment status，income，and social security exclusion in cities，and on the other hand，by family life，family labor size and land acquisitions in the villages. Return migration is a combined result of“active return”and“passive return”，and of individual and family decision making. The authors analyze the positive effects of return migration，resulting in Brain Gain based on migrants' human capital accumulation during their migration. Returned migrants are more likely to engage in non-agricultural activities and self-entrepreneurship. Migration and return migration jointly help mobilize labor market and promote rural-urban development in China.

One of the most important tasks of urbanization in China today is to accelerate large amount of migrants integrating into urban society．Different from existing researches which focus on hukou system and institutional reforms，this paper emphasizes the role of social capital and social mechanism in improving social integration of migrants，calling for a closer relationship between migrants and urban local residents．Improving the quantity and quality of Localized Social Capital ( LSC) would be a crucial factor contributing to social integration of migrants．The paper defines and measures LSC in three dimensions: Social Participation ( SP) ，Social Trust ( SC) and Social Intercourse ( SI) ，and analyzes how those LSCs have influenced social integration of migrants．While SP and ST have significant effect on migrants’social integration，the effect of SI is not significant．The paper discusses policy implications for enhancing migrants’LSCs to promote their social integration: encouraging more social participation and involvement in public affairs; cultivating mutual trust between migrants and local residents; and developing more positive intercourse and communications between migrants and local residents．

 Social Integration for migrants is a combined process of increasing assimilation and reducing exclusion,and a process of coordinating expectation of migrants and acceptance of urban sector,and a process of developing counter relations and building social network among migrants and local people.The paper measures social integration degree of temporary migration in four dimensions,including identity recognition,expectation to city life,interaction with local residents and feeling of social attitudes from local citizens.Results show that various variables have different impact on different aspects of social integration.Based on a regression model,the paper tests three hypothesis on the factors associated with social integration of migrants:migrant individual and family characteristics are significantly associated with social integration;community participation and social capital significantly associated with social integration;and institutional arrangements significantly associated with social integration.In improving social integration of migrants,the paper argues for comprehensive policies addressing the variety and complexity of the process of social integration,including those towards natural integration and interventionary integration,active integration and interactive integration,and promoting a gradual and multidimensional integration process.