With the gradual promotion of governmental service purchase of social workers, the interactive relation between government and social work agency becomes direct, frequent, complex and subtle. In item procurement spots, the government and the social work agency launch continuous gamble on resources, power and major. In this process, the two parties have each own acting logic but tend to strategically cooperate, however, strategic cooperation is not simply expressed as cooperation, the dynamic state of the interests orientation and the interactive relation of the two parties determines the complexity of the strategic cooperation, among which the resources dependence make social work agency stay at absolute weak position in the strategic cooperation, which affects the independence of its major and development. China should perfect governmental purchase mechanism to realize double-direction construction of the government and the social work agency, and finally construct a kind of “partner relation” of the two parties with cooperation in independence.