Objective To study the application effect of PDCA quality control cycle method in outpatient pharmacy management and its influence on drug management defects. Methods From January to December 2021, 500 prescriptions of outpatient pharmacy randomly selected from Huadu District People's Hospital of Guangzhou were classified as pre-management group, and routine management was implemented. From January to December 2022, 500 prescriptions of outpatient pharmacy randomly selected from Huadu District People's Hospital of Guangzhou were classified as post-management group, and PDCA circulation method was implemented. The prescription quality defects, the qualified rate of drug management and the incidence of drug management defects were compared between the two groups. Results The incidence of quantity error, variety error, lack of drugs and other items in the post-management group was lower than that in the pre-management group (P<0.05). The qualified rates of quantitative management, appointment management, regular inspection, location storage and validity management of outpatient pharmacy in the post-management group were higher than those in the pre-management group (P<0.05). The incidence of drug management defects in the post-management group was 3.00%, which was lower than 7.20% in the pre-management group (P<0.05). Conclusion The application of PDCA circulation method in the prescription management of outpatient pharmacy can effectively improve the qualified rate of drug management and reduce the incidence of drug management defects.