Objective: To examine the E coli and K pnenmoniae strains' resistance to the third generation cephalosporins and to understand the production of extended-spectrum β-lactamaes. Methods: The MIC of seven antibiotics to 49 E Coli and 35 K pneumoniae were detected by MH broth dilution. Results: The MIC of IPM is as low as 4 μg/ml,with excellent antibacteria effects.The resistance percentage of CPZ to E Coli was 61.2% while that to K pneumoniae was 20%,but the resistance percentage of SPZ was lowered to 6.1% and 8.6% respectively.The other cephalosporins' resistance rate varied from 10% to 35%,the typical bacteria which produces ESBL was E Coli and the positive rate was 11.9% when ESBL was used as reactive substance to detect ESBL.Conclusion: Much attention should be paid to the choosing of the third generation cephalosporins.