Abstract: Using CTX-M type extended spectrum 茁- lactamases （ESBLs） producing Escherichia coli （E. coli）, the present study investigated the antibacterial effect of banana straw water extracts combined with ant imicrobial agents in vitro. The minimum inhibitory concentrations （MICs） ofbanana straw waterextracts and the 19 selected antimicrobial agents （amoxicillin, amikacin, fosfomycin, enrofloxacin, mequindox, azithromycin, rifampicin, sulfamonomethoxine sodium, ceftiofur sodium, etc.） against the CTX-M type ESBLs producing E. coli were determined by using broth micro-dilution method; the antibacterial effect of banana straw water extracts combined with each of the 19 selected antimicrobial agents against the CTX-M type ESBLs producing E. coli was assessed with checkerboard micro-dilution method, and the fractional inhibitory concentration index （FICI） was used to evaluate the interactive effect between banana straw water extracts and different antimicrobial agents. The results showed that when banana straw water extracts were used with mequindox or fosfomycin, FICI ≤ 0.5, indicating a synergistic effect; when banana straw water extracts were applied with ceftriaxone sodium, ceftazidime, ceftiofur sodium, cefotaxime, amoxicillin, sulfamonomethoxine sodium, azithromycin, florfenicol, or rifampicin, 0.5 〈FICI 臆 1, indicating an additive effect; when banana straw water extracts were employed with ciprofloxacin, levofloxacin or lincomycin, 1〈FICI ≤ 2, indicating an independent effect; when banana straw water extracts were used with clinafloxacin or gatifloxacin, FICI〉2, indicating an antagonism effect. Our results demonstrate that the banana straw water extracts improve the antibacterial effect of some antimicrobial agents against the CTX-M type ESBLs producing E. coli.