Abstract: OBJECTIVE To study quality controllability of determination method of related substances of norfloxacin capsules in Chinese Pharmacopoeia(2015 Edition)(ChP2015) and to improve the current method. METHODS The related substances of 57 batches of norfloxacin capsules samples from all regions of Zhejiang province were determined according to ChP2015 method and EP9.3 method, and the results were compared. The rationality of the ChP2015 method was discussed. RESULTS The tested results of 57 batches of samples according to EP9.3 method showed that the contents of impurity E of 5 batches of samples exceeded the limit(0.15%), and the impurity K of 1 batch of sample was on the edge of the limit(0.15%). While the results of 57 batches of samples all met the requirements according to ChP2015 method. The method of related substances of Norfloxacin capsules in ChP2015 was not specific, and the impurity E included in the main peak was difficult to detect. The determination results were affected by the columns of different brand and the mobile phase conditions in ChP2015 method of related substances. Using Waters Sunfire C₁₈ column and adjusting the proportion and gradient condition of the mobile phase could make the impurity E well separated from the main peak of norfloxacin, the determination results of samples were in accordance with EP9.3 method, and it could control the impurity E, K and other impurities. CONCLUSION The contents of impurity E of norfloxacin capsules exceed the standard on the current market of Zhejiang province, and it can not be detected according to ChP2015 method. The determination method of related substances of norfloxacin capsules in ChP2015 can not control the quality of the drug effectively and need to be revised and improved.