China's large-scale internal migration has stimulated ongoing debates about consequences of geographical mobility for population health. Although existing research predominantly focused on migrants' health in host societies, the complex relationship between migration and health throughout the full migratory cycle remains understudied. Analysing data from 2010 China General Social Survey (N = 1,660), we investigate variations in migrants' physical and mental health across four distinct migratory stages—intended, temporary, permanent, and return migration. Supporting the “healthy migrant” and “salmon” hypotheses, we found that intended migrants have better health than rural residents with no migration intention, and migrants have better health than return migrants. The health disparity between nonmigrants and migrants is largely explained by selective demographic and socio-economic traits, but not health behaviours. Rural-to-urban migration is associated with adverse health outcomes, particularly among permanent migrants. The findings suggest potential health risks associated with rural-to-urban migration and migrant assimilation in urban China.