Since borrowed from foreign countries, social work in China has undergone a long process including introduction, adjustment, and localization to function. However, among current studies on social work, theoretical analysis about this process barely existed. Based on the Ecosystem Theory, this paper divided this process into three stages: 〖JP2〗integration to acquire position, mutual help to solid position, and showing the ultimate value to become professionalization. According to this, this paper selects three concepts: integration, symbiosis, and competition to show the contents of each stage. These stages rely on each other and develop gradually. If professionalization is regarded as the symbol of maturity of social work in China, the process of professionalization reveals the interaction and gradualism of these three stages. Furthermore, the whole process of the development of social work in China also reflects this. Because of the developing gradualism, this progress can be found in current micro affairs of social work.