Objective To analyze the causes of drug dispensing errors and reduce the error rate through scientific precautions, and improve the quality of pharmaceutical service. Methods According to the PDCA cycle, existing problems were found in dispensing between January and June 2013, and the causes were analyzed. Then, from July 2013, strategies were developed to decrease the dispensing error rate. The variation trend of dispensing error rate from January 2013 to June 2017 were observed. Result The dispensing error rate decreased since the beginning of PDCA cycle, from 0.042‰ (the first quarter of 2013) to 0.003‰ (the second quarter of 2017). Conclusion The PDCA cycle is an effective intervention to detect the errors during drug delivery in inpatient pharmacy, which could improve the quality of pharmaceutical service and insure the patients’ safety.