Abstract: In order to explore the effects of antagonistic bacterium treatment on the preservation effect and protective enzyme activity of muskmelon, this study selected Xizhoumi 25 melon as the research object, and inoculated the melon surface with Bacillus velezensis BG-2 at 25 ℃ and 4 ℃. The colonization characteristics, preservation effect, peroxidase (POD), polyphenol oxidase (PPO) and phenylalnine ammonialyase (PAL) of antagonistic bacteria on melon surface during storage were determined. Under the conditions of 25 ℃ and 4 ℃, the number of antagonistic bacteria on melon surface increased firstly and then decreased. The fresh-keeping effect, pH and soluble solid content decreased of muskmelon inoculated with antagonistic bacteria were significantly better than those of control group. POD and PAL activities increased first and then decreased, PPO activity increased first and then decreased at room temperature, and slowly increased at 4 ℃. At 25 ℃, the enzyme activity of POD, PAL and PPO in antagonistic treatment group was the highest on the 20th day, and the highest on the 10th day. Under 4 ℃, POD and PAL activity were the highest on the 20th day. The highest enzyme activity on the 40th day of PPO treatment. The enzyme activity of the antagonistic bacterium treatment was always higher than pathogen treatment. Bacillus BG-2 could stably colony on the epidermal of muskmelon at both 25 ℃ and 4 ℃, inhibited the decaed of muskmelon during storage, delayed the decreased of pH, soluble solids content, POD, PPO and PAL enzyme activities, and the combinated of BG-2 and low temperature had better effect on the above. This study provided a theoretical basis for prolonged the storage period of Xinjiang muskmelon and provided technical support for the antagonistic bacterium effect of muskmelon after harvest.