Objective:To study and evaluate the protecting effect of levofloxacin hydrochloride on systemic infection in mice. Methods :960 mice were used

and divided randomly into 96 groups. Certain amount of E. coli

S. aureus

P. aeruginosa and S. flexneri were administered respectively into the mice and all of them were infected. Immediately after being infected

each group of mice were given different doses of intravenous or oral levofloxacin hydrochloride and of loxacin

in order to determine the protective effect of levofloxacin hydrochloride on the mice infected with these four bacteria. Results: The intravenous injection of ED50 of levofloxacin hydrochloride to the bacteria strains was 0.359mg/kg

5.848mg/kg

22.894mg/kg and 0. 371mg/kg respectively;and ED50through the oral route was 0. 554mg/kg

8. 129mg/kg

28. 895mg/kg and 0. 492mg/kg respectively. Conclusion :The protecting effect through intravenous injection of levofloxacin hydrochloride on systemically infected mice is more superior to that of the oral route

and also better than ofloxacin.