The aim of the research was to study the stability of mezlocillin sodium and sulbactam sodium for injection dissolved in three injections such as glucose, sodium chloride or glucose and sodium chloride at 25°C. The samples from these solutions were collected at the different time and the contents of mezlocillin sodium and sulbactam sodium and impurity were determined by HPLC. The pH values of the solutions were also measured. The pH values varied slightly in acceptable range and the contents of mezlocillin sodium and sulbactam sodium varied as well within 12 h. Mezlocillin sodium and sulbactam sodium for injection were compatible with three injections. The contents of mezlocillin sodium and sulbactam sodium in the prepared solutions were stable and the impurity contents in the solutions were slightly increased within 12 h under the experiment condition.