AIM: To study the compatible stability of cefepime with 0.5% metronidazole injection.　METHODS: Dual wavelength spectrophotometry and K-ratio spectrophotometry were described for the determination of cefepime with metronidazole injection during 6 h. 　RESULTS: There was no evident variation in content during 6 h at room temperature. The average recovery rates of cefepime and metronidazole were (100.9±0.4)% and (99.8±0.6)% (n=5).　CONCLUSION: The compatiblity of cefepime with metronidazole injection is stable. The method of using dual wavelength spectrophotometry and K-ratio spectrophotometry to determine the compatible stability of cefepime with metronidazole is simple, accurate and usable.