Objective:To explore the interaction effectiveness of residence and social support on physical function for older adults.Methods:Using multistage sampling method, the older adults in 9 provinces were chosen to investigate from January 2022 to January 2023 by using general information questionnaire and Short Physical Performance Battery.Binary Logistic regression analysis was used to explore the independent effectiveness of social support and residence category on physical function.The additive and multiplicative models were used to analyze the interactions between above two factors.Results:A total of 23 922 older adults were investigated.And 18 719(78.3%)older adults had poor physical function.There were significant independent effect of social support and residence category on physical function of older adults( P<0.001). Besides, the results showed that residence category and social support had a significant multiplicative interaction on physical function( OR=0.763, 95% CI: 0.615-0.947, P=0.014). The crossover analysis showed that older adults living in rural as well as lack of social support had the highest probability of impaired physical function( OR=1.521, 95% CI: 1.308-1.769, P<0.001). But there was no difference found in additive interaction. Conclusions:An interaction effect was found in rural living and lack of social support.Older adults living in rural as well as lack of social support have a higher risk of impaired physical function.