Kaohsiung-Pingtung area covers Kaohsiung City, Kaohsiung County, and Pingtung County. Unbalanced resource allocation results in retard development in south area compared with north area in many respects, including the operation of social structures. This phenomenon might results from the social development modality of south area, that is, a family business factional model, which influences the local development policy with its patron-client relationship. Even though factions today are gradually decline, they still have a great impact on various fields of the society. Factionalism controls the balance of local resources, and affects the resource allocation and policy of sustainable development in the south area. This research aims to use the cognitive judgment of ”Social Judgment Theory” (SJT), to investigate the influence of factionalism on sustainable development in Kaohsiung-Pingtung Area. We found out factionalism wasn't all negative power to area for sustainable development. Positive factionalism way was good for Kaohsiung-Pingtung area political operation and social development.