Abstract: The article studies the social security (mainly for social insurance) of the floating population in Beijing using the data of "one-per-thousand floating population of Beijing sampling survey in 2006".From the aspects of personal characteristics, occupational characteristics, family characteristics and the degree of government regulation, such conclusions are drawn as follows:in the personal characteristics, hukou will affect the insurance rate;the education level has a positive but not linear effects on the rate of pension insurance and of unemployment insurance;for the work status perspective of the floating population, the employees have higher medical insurance and unemployment insurance needs than the employers, and the self-employed;the wage level and training level both have positive relationship with the purchase of various types of insurance;many variables describing the extent of government regulation have no significant impact on the floating population's inclining to the insurance.As the social security is public goods, the government should give more supports.