This study explored the antibacterial effect of nisin (NIS) combined with meropenem (MEM) on methicillin resistant Staphylococcus aureus(MRSA).The minimum inhibitory concentration (MIC) was detected by micro broth dilution method,and the fractional inhibitory concentration index (FICI) was calculated by chessboard combined bacteriostasis test to evaluate the inhibitory effect.Crystal violet staining test was used to quantitatively detect the effect of drug combination on the biofilm formation of MRSA isdates.Galleria mellonella model infected by different treated MRSA was established to compare the survival rate.The results showed that the combination of MEM and NIS had synergistic inhibitory effects on the tested three MRSA strains,and the FICI values were 0.375,0.5 and 0.375 respectively.After 6 hours of treatment,both the combination group (MEM+NIS) and the NIS group could inhibit biofilm formation without statistical difference (P > 0.05).The survival rate of G. mellonella showed that after five days,the survival rates of larvae infected by three MRSA strains were 30%,80%,and 30% respectively.For strain Yn2020051 and Yn2020078,the MEM+NIS group had higher survival rate than that of NIS group,MEM group and positive control (PC) group (P<0.05).