The traditional dual social security system determines the great benefit gap between urban area and rural area.Eliminating completely such kind of difference is impossible in the short term.Thus the possible strategy in rapid urbanization process is to construct a transition-type system which we call peasant-municipal social security system.It serves an institution evolution ladder which aims finally achieving integrated urban-rural social security system.In this paper, we take Shanghai Pudong New Area as a case study to show empirically how this strategy works.