Abstract: Objective To expand the experimental data and re-evaluate the special safety of Mezlocillin Sodium and Sulbactam Sodium for Injection. Methods The inspection of hemolysis and cohesion through in vitro hemolysis test, the vascular irritation of rabbit auricular vein, and passive cutaneous anaphylaxis were carried out with different concentrations of Mezlocillin Sodium and Sulbactam sodium for Injection in saline solution, which pH value, particulate matter and osmotic pressure molar concentration (OPMC) were determined according to the methods in the appendix of Chinese Pharmacopoeia 2010 Part II, as well. Results Mezlocillin Sodium and Sulbactam sodium for Injection had no vascular irritation and injury effect on rabbit vascular endothelial cell, and no evidences of hemolyzation and aggregation on rabbit erythrocyte at required clinical concentration, whereas the vasculitis and thrombosis were observed when this concentration increased. Since the particulate matter and OPMC exceeded the standard only when more than 10 times of its clinical concentration, the damage must be caused by the drug itself. No allergic reaction on guinea pig skin was observed at the maximum tolerated dose. Conclusion The results of special safety tests fit the new drugs application requirement at clinical concentration. This concentration should be strictly followed in clinical use to prevent from the damage of erythrocyte and endothelial cell by the drug itself. It is necessary to expand the special safety tests.