Objective To evaluate the in vitro activity of cefazolin penta-hydrate and other common used antimicrobial agents against clinical pathogens isolated within last 3 years. Method MIC values were deter-mined by standard twofold agar dilution method. Time kill curves were il-lustrated by colony form unit (cfu) count method. Totally , MICs of 604 isolates within last 3 years from 19 hospitals were tested. Result The results indicated that for Gram - positive aerobic pathogens, cafazolin pentahydrate showed satisfied in vitro activity against methicillin suscepti-ble Staphylococcus aureus ( MSSA), methicillin susceptibel Staphylococcus epidemidis (MSSE), penicillin susceptible Streptococcus pneumonies (PSSP) and Streptococcus spp. β-hemolytic group. MIC90 was ≤ 4 mg · L-1 For Gram- negative bacilli, cefazolin pentahydrate also showed antibacterial activity. MIC values was ≤ 8 mg · L-1 for non- ESBLs Enterobacteriaceae bacteria. Time- kill curves test results indicated that cefazolin pentahydrate typically is of time dependent profile against staph-ylococci, but for E. coli, the bactericidal activity slight increased with drug concentration increased. Conclution Compared with contrast drugs, the activities of cefazolin pentahydrate against G+ bacteria were better than cephalexin, clindamycin, clarithromycin, and silght better than cefotiam, and similar with amoxicillin/clavulanic acid, cefuroxime and levofloxacin. For non - ESBLs Enterobacteriaceae, the activies of cefazolin pentahydrate were better than cephalexin, and similar with amoxicillin/clavulanic acid and cefuroxime.