Abstract: Children aged 7 to l5 were individually interviewed by the dilemma story of promise-keeping for investigating children's development of understanding of friendship. The results showed:1.The understanding of friendship was conditioned by the abilities of differentiating and intergrating oneselfs and other's social perspectives and development of the moral norms such as altruism and promise keeping. In the view of the structural development a scoring manual was developed. Four levels were identified in the children aged 7 to 15: Material orientation level(Level 0); Prenormal level(Level 1); Normal level(Level 2) and conceptualized level(Level 3). There were also some transitional levels between two levels designated to level 0/1,1/2 and 2/3,Most 7 year olds were in level 1 or 1/2; most 9-year-olds in level 1/2 or 2; most 12-year-olds in level 2 or2/3; most 15-year-olds in level 2/3 or 3.2. The qualities of formal schooling and the levels of parents' educational background had strong effects on the development of understanding friendship in the children, however those effects became weakened with increase of age. The levels of logic-physical cognition and general intelligence were also relevant to the development concerned. 3 There were some differences compared with the findings of literature in western societies, the dominated motivations for dealing with the friendship issue in Chinese children were not egoism but altruism which were attributed to the effects of education and traditional cultural values.

Key words: children aged 7 to 15, social cognitive development, friendship, dilemma story