The changing trends of antibiotic resistance of Proteus mirabilis isolates were compared. A total of 288 Proteus mirabilis isolates obtained from clin. patients in The First Affiliated Hospital of China Medical University between 2001-2006 were included in the study. K-B test was used to determine the susceptibility and the results were read based on National Committee for Clin. Laboratory Standards (NCCLS) of the USA. The sensitivity of Proteus mirabilis isolates to imipenem, ceftazidime, cefotaxime, aztreonam, cefoperazone, tazobactam, cefepime, amikacin and piperacillin was from 74.5% to 95.2%, meanwhile, there was a low sensitivity to ampicillin, cefazolin, ciprofloxacin, sulfamethoxazole co. and tetracycline, from 2.3% to 58.8%. The result of antimicrobial susceptivity test may instruct the application of clin. antibiotics.