Human behavior in community is probably shaped by subculture differences on individualism/collectivism. The paper developed triple-line theory to explain collectivism variations within China mainland from both natural and societal ecological perspective. China could be divided into four regions by Hu Huanyong Line and Great Wall Line and Qinling-Huaihe Line. Then evidence-based researches are summarized to support triple-line theory. Finally，we discuss a few themes deserved to be done in future.