This paper reveals the mechanism of population migration along the coastal urban regions in China. This is the first large scale survey on floating population ever conducted in large and medium cities including Beijing, Tianjin, Tangshan, Langfang, Nanjing and Kunshan. The paper first reviews the intellectual foundation of demographic studies on migration. With the survey data and further analysis, it examines the characteristics of population migration in Chinese cities. China is now undergoing a large scale of rural migration into the urban domain with mechanistic increases in the number of floating population. The motive for migration is predominately economic. Family type migration is getting more popular than individual migration. From an economic perspective, low value added, semi skilled jobs are taken up by the first time migrants, and there is also the corresponding shift to service and managerial type of work for the local residents. Chain type migration with upward movement on the job ladder is observed for the second time migrants. From a social viewpoint, jobs for migrants are mostly untenured and without welfare provision as compared with those available for the urban dwellers. Migrations in cities coalesced together to form cliques and syndicates. This has resulted in a more segregated urban morphology.