OBJECTIVE： To observe the stability of mezlocillin sodium in 5％ glucose injection， glucose and sodium chloride injection and maintain solution for infants injection with different pH， over different periods and at 4℃ ， 25℃ ， 37℃ .METHODS： 9 solutions with different pH were made up by mezlocillin sodium and above-mentioned infusion fluids， according to 4 factors and 3 levels to make L9（34） orthogonal test.Then determination of mezlocillin sodium in each solution was carried out with ultraviolet spectrophotometry.RESULTS： The contents of mezlocillin sodium in above-mentioned solutions with different pH and at different temperature have not changed obviously over 0h-8h.CONCLUSION： Mezlocillin sodium is compatible with above-mentioned solutions.