Abstract: In order to understand the characteristic of change of MICs of different antimicrobial agents against the resistant E. coli strains induced by certain antibiotics in vitro, induction experiment of E. coli ATCC 25922 was conducted using tetracycline hydrochloride, ciprofloxacin hydrochloride, sodium salicylate and chloramphenicol as inducers by 1/2×MIC method. Prior to the induction experiment, the tested strain was morphologically and biochemically identified. During the induction experiment, the tested strains were morphologically identified. The MICs of 16 antimicrobial agents against the quality control strain were determined ahead of induction, and the MICs of 16 antimicrobial agents against the 4 induced strains were also determined when the concentrations of inducers reached to 128×MIC. The results showed that the morphological and biochemical characteristics of the tested strains were identical to E. coli. Before induction, the MICs of 16 antimicrobial agents against the quality control strain ranged from 0.25 to 64.00 μg/mL. MICs of cefotaxime, tetracycline hydrochloride, oxytetracycline, thiamphenicol, norfloxacin, cefoxitin and some of other antibiotics against the tetracycline hydrochloride induced strains were increased by 4 fold or more than 4 fold compared with those against the quality control strain, which showed a statistical significance. While MICs of cefotaxime against the ciprofloxacin hydrochloride induced strain and chloramphenicol induced strain were increased by more than 4 fold compared with that against the quality control strain, no statistical significances were found in the change of MICs of other antibiotics against the ciprofloxacin hydrochloride induced strain and chloramphenicol induced strain. When the concentration of sodium salicylate exceeded 16×MIC, the induced strain were not able to grow. It was indicated that the change of MICs of the tested antibiotics against the tetracycline hydrochloride induced strain was most obvious, and the E. coli was prone to become resistant under the selective pressure of tetracycline.