Nowadays China is expiring a deep social transit ion. Matching with social transition, the government proposed a scheme to build a well-off society in an all-round way in the first 20 years of the 21st century. The keystones and the difficulties are in the rural area. The factors to restrict the target realization are the economic unbalance and the consequent lag of social security in the rural area. Therefore, we have to strengthen rural social security system.