Abstract: OBJECTIVE To study the compatible stability of cefoselis sulsate with metronidazole injection. METHODS The content of the mixture of cefoselis sulsate and metronidazole within 8 h were determined by HPLC, meanwhile the changes in appearances and the pH values were observed. RESULTS The content of cefoselis sulsate and metronidazole injection was stable within 8 h. The mixture was clear, pH value was also stable. CONCLUSION Cefoselis sulsate can be mixed with metronidazole injection for clinical use.