Objective To understand the status of social participation of the elderly in long term care institutions and analyze its influencing factors. Methods A cross-sectional study was conducted among a convenience sample of 243 residents in long term care institutions in Chongqing. A demographic questionnaire, the Barthel Index, the Chinese version of Impact on Participation and Autonomy Questionnaire (IPA), the Social Support Rating Scale and the Attitudes to Ageing Questionnaire were used to survey the residents. Results The nursing home residents scored (31.70±15.52) points in social participation. Multiple linear regression analysis showed that self-care ability, attitude towards aging, economic status and objective social support were influencing factors of social participation (P<0.01 for all). Conclusion Social participation of the elderly in long term care institutions need to be improved. Long term care institutions should pay attention to residents′ social participation level and develop targeted interventions according to the influencing factors, so as to improve the level of social participation of the elderly.