Objective To investigate the influencing factors in the service volume of primary health care institutions in Chengdu, and provide references for promoting the hierarchical diagnosis and treatment. Methods A self-administered questionnaire was used to investigate the service volume of a total of 390 primary health care institutions (including community health service centers and township hospitals) across 22 districts and counties of Chengdu from October to November 2016. Rank sum test, rank correlation analysis and multiple linear regression model were used to analyze the influencing factors of outpatient visits in the institutions. Results The median annual amount of outpatient visits was 60 493 in community health service centers and 31 374 in township hospitals. Between community health service centers and township hospitals, the difference in median daily visits per doctor was not significant (14.41 vs. 13.29), but the median daily visits per doctor in general practitioners (12.22 vs. 8.16), rehabilitation physicians (10.10 vs. 6.34) and traditional Chinese medical doctors (4.82 vs. 6.17) varied considerably. Multiple linear regression analysis showed that the amount of outpatient visits in community health service centers was related to the amount of intermediate physicians, while the amount of outpatient visits in township hospitals was related to the setup of dental clinics, the amount of primary physicians, the amount of beds and population to be served (P<0.05). Conclusions Differences exist in the service volume among primary health care institutions in Chengdu. It’s necessary to make proper plans for the management of administrative offices and the allocation of personnel, so as to improve medical services of primary health care institutions.