Using microcosmic data of 2010 census,this paper studies the impact of air pollutant PM _2.5concentration on household decisions about migration from the perspective of household units.Reverse causality between PM _2.5concentration and household migrations are investigated by means of instrumental variable method,and the possibility of family migration with children and old people respond to PM _2.5pollution is also explored.The results show that mean PM _2.5concentration and cumulative average PM _2.5concentration of three and five years before the migration year have a significant "promotion" effect on family migration behaviors.The study also finds that when there is higher PM _2.5pollution,families tend to migrate together with vulnerable groups ( elder people and children) who are vulnerable to PM _2.5pollution.The possibility of family tendency to migrate in the face of worse PM _2.5air pollution was greater.In addition,this paper proves that there is a causal endogeneity between PM _2.5concentration and family migration behaviors,which underestimates the estimation coefficient.Demographic dividend is one of the key factors in the sustainable development of a city.In the future,with urbanization and scarcity of population dividend,local governments should introduce corresponding measures in the aspects of public environmental policies,infrastructure investments and constructions,and coordinated development strategy of social security for displaced populations.