As important components of Beijing resident population，migrants’ vital interests are closely related to their social security issues. The paper discussed the current situation and influencing factors of the social security of migrant workers in Beijing，using an empirical approach with data from workers in life service industry. We find that variables like gender，household type，education，occupation certificate，work years at the current company and monthly income，have great impacts on migrant workers’ participation rates in the endowment insurance，medical insurance，unemployment insurance，work injury insurance and maternity insurance. Participation enthusiasm of this group is largely subject to restrictions of their high mobility，limited knowledge on social security policy and the social security transfer between two different places.