The paper reviews and studies main practice and experiences of encouraging immigrants integrating by some famous world metropolis.It proposes that following points can give us some suggestions:① Integration is not assimilations, we can measure social integration by whether entitled the citizenship or not。② Integration policies should emphasis the identity, language, education, employment and social space construction。③ Police should pay more attention to better the social integration of the second generation of immigrants。④ Education for the second generation of immigrants is very critical for them to integrate into the city。⑤ The local authorities should help immigrants integrate into the city with encouraging policies. <<