Based on the data collected through three surveys on urban family in China,we examine the change of the family structure and the factors which have effected on it from both point views of social change and family life cycle.The main finding of the data analysis is that change of family structure with the change of family life cycle in the different time is the same.According to this finding,we think that the social change is not the only factor,that has an effect on the change of family structure.The change of family life cycle is another important factor,which has effect on the change of family structure.In another words,to know the pure effect of social change on the change of family structure we must control the change of the family life cycle.