Abstract: The United States is a multi-ethnic immigrant country， and the study of ethnic relations is the subject of Park’s “Human Ecology”. According to his sequence of “race relations cycle”， Park sees that the Old World is stagnant in the “preliminary stage” of competition and conflict， and thus pins his hope on the “climax stage” of accommodation and assimilation in American society. The transformation of these two stages is accompanied by the natural process of “succession” of social forms. However， the ultimate ideal of assimilation is always out of reach， and the hybrid state of symbiosis is an established social fact. The paradox is that Park does not find this unbearable. Because of his unique background， Park sympathies with minorities and that leads to a “cosmopolitan” sociological imagination. Regrettably， the ecological order， organized solely around the economy of nature， lacks the familiar ground that can make social life tolerable for immigrants. Immigrants， who come to the New World from all corners of the world to seek their destiny， are from different ethnic origins and bear different cultural imprints. Even if they find a place in urban life， they can hardly feel at home. Immigrants have long left behind a traditional family-centered and outward-expanding order in an effort to adapt to a symbiotic world of economic interdependence and emotional isolation. If the migrants in Chinese cities do not become “strangers” suffering from “wanderlust”，it may be because they still have a “home” in their hearts. Because they always have such a concern deep in their hearts it allows them to be moving around in strange places without wandering. This is completely different from the cosmopolitan American society.

Key words: human ecology, succession, symbiosis, cosmopolitanism, city