Government policy for rural-urban migrant workers in China has been undergoing great changes since early 2000. In the 1980s and 1990s, the Chinese government excluded this group from the urban social protection system, but since early 2000, rural-urban migrant workers have gradually been included in some urban social programs. This study aims to explain this policy change and explore its effects. Both documentary analysis and case study research methods have been employed to fulfill this task. Government documents and other secondary data are examined first to provide explanations for this policy change. A case study in one city of China, namely Tianjin, was conducted to find out the effects of the policy change on rural-urban migrants’ welfare and their migration patterns. It is hoped that this study can help to enhance international understanding about the situation of rural-urban migrants and relevant policymaking in contemporary China.