Objective To explore the influencing factors of physical activity (PA) among pregnant women and to provide reference for formulation of PA enhancement strategies for pregnant women. Methods A total of 15 pregnant women were approached for semi-structured interviews by using a pre-set interview outline.Based on the socioecological model, the data were analyzed by using content analysis. Results A total of 3 themes and 12 subthemes regarding the influencing factors of PA were extracted:influencing factors at the individual level included planned mode of delivery,benefits and risk perception, knowledge of PA during pregnancy,disturbance of pregnancy symptoms, and PA self-efficacy; influencing factors at the interpersonal level included family support, peer support, and professional support; influencing factors at the environmental level included natural environment, built environment, social culture, and PA promotion services for pregnant women provided by the community or health facilities. Conclusion PA of pregnant women is affected by multi-level factors.Intervention measures at the individual, interpersonal and environmental levels are suggested to improve PA level of pregnant women.