Abstract: Peasant laborer's social mobility is not only a process of economic activity, but also a process of origination, development and successive variation of new social relations. Ningbo carried on the system reform against social exclusion in the initial period of immigration, so that immigrating peasant laborers have the equal social status with the local residents. The practice in Ningbo tells us: social relations evolution of immigrating peasant laborers depends on not only the reform of external social conditions such as system establishment, policy arrangement and so on, but also the on enhancement of immigrating peasant laborers' individual quality after migration. Only when both sides interact well can the social harmony be achieved.