Abstract: OBJECTIVE To study the compatibility of penicillin for skin test with 0.9% sodium chloride, to verify the rationality of current drug use instruction. METHODS Three batches of penicillin for skin test were prepared into solution according to current drug use instruction, and stored for different period under different temperature, evaluating the change in related substances and assay for different storage period by HPLC. RESULTS The related substances in penicillin for skin test dissolved in 0.9% sodium chloride tend to rise over time:at the room temperature of 25℃ for 4 h, total impurities were close to 1.0%;at the room temperature for 8 h, total impurities were close to 2.0%, and obviously exceed the in-house specification (1.0%);at the low temperature of 2-8℃ for 24 h, total impurities were <1.0%. CONCLUSION The compatibility stability of penicillin for skin test with 0.9% sodium chloride is closely related to storage temperature and time. It is suggested that during clinical use, prepared penicillin solution for skin test shall be used within 4 h at about 25℃ and within 24 h at 2-8℃. The enterprises shall revise the drug use instruction of penicillin for skin test in time, stating the storage temperature and time under the usage and dosage, in order to ensure the accuracy of skin test and safety of drug.