Abstract: 　Based on the practice of social service program purchased by the municipal government in City B, this paper analyzes the operating logic of contractual relationship from the present relationship of power restrictions. First, it divides the contract relationship’s characteristics into four types, collaborating, helping each other, conspiring, and incubating. Secondly, the two parties of the contract differ in economic interests, value concept, management style of the key persons and the degree of maturity of the organizations, which contribute to the difference in their contractual relationship. Contractual relationship not only refers to the contract relationship regulated on the paper, but also the factual relationship of dominating and being dominated, which reveals the strong operating mechanism of street government-corporatism. Whether the practice of government purchasing services can get the expected results depends on the establishment of a game system of balancing interests.

Key words: government purchased services, contractual relationship, corporatism