Using the China Household Income Project migrant survey data from 2007 to 2008, this paper examines the association between migrant workers' labor contract status and their social insurance participation, including pensions, work injury insurance, unemployment insurance, medical insurance, and the housing provident fund. The results show that having a labor contract, especially a long-term contract, improved the migrant workers' social insurance coverage to a substantial extent. Furthermore, moving from having a short-term contract or no contract to having a long-term contract significantly increased one's odds of having social insurance, whereas losing a long-term contract reduced the likelihood of having social insurance. These results highlight the importance of having a long-term labor contract for migrant workers' ability to obtain social insurance coverage and thereby increase their security and protect their basic rights. (C) 2012 Elsevier Inc. All rights reserved.