The frequent occurrence of group events is one of the main types of social conflict of reservoir resettlement. Hence, it is of great significance to analyze the occurrence process in order to manage and deal with group events. Taking the conflict event between F village's resettlement and government organization for example, the paper uses process-event method to analyze the occurrence process of resettlement conflict from the perspective of clash between migrants' rationality and the state's law. According to the research, in the whole process of embryo, formation, breaking and upgrading of the conflict, the migrants' rationality keeps clashing with the state's law and finally leads to the breaking and upgrading of the conflict. Then the paper summarizes the occurrence process of the resettlement conflict and the model concerned.