This paper puts forward a model for the appraisal of hazard degree of pollution origins in oilfield development which combines fault tree analysis and gray connection degree analysis. By using gray connection degree analysis method, it identifies the accident modes. Besides, it  analyzes and derives the occurrence probability of various fault models of the top event according to a certain concrete fault tree. The paper makes an empirical study on the classical case of Daqing Oilfield Engineering Cooperation, which proves the feasibility of this method in appraisal of hazard degree of pollution origins in oilfield development.