This study aimed to explore the willingness of using physical activity smartphone apps among patients with chronic diseases. 218 outpatients from a tertiary hospital in Beijing were involved using a questionnaire. Over half of the patients (53.7%) were willing to use smartphone apps to promote physical activities. The individuals more likely to use physical activity apps tended to be younger (≤44 years), be more educated, perceiving their disease need exercise instruction or professional support, current smartphone user, having previous experience of using physical activity apps, and accepting paid apps (P<0.05). The results could help health educator suggest chronic disease patients to use apps to do more exercises. Further research could be focus on evaluate the effects of using physical activity apps in chronic disease patients.