Abstract: The effect of chitosan on the preservation and antibacterial effect of carambola was studied. In this experiment,chitosan of housefly larvae was degradated to get soluble chitosan. The study was divided into five groups:blank group,positive control group,0.5%,1%,2% chitosan group. Every day their weight was measured,their maturity was observed and their content of vitamin C and total sugar after 9 days was measured.Aantibacterial activities of extraction were tested by the filter paper method of four G+and G-strains. It illustrated that the extraction rate of soluble chitosan from housefly larvae was about 29.70% and chitosan could be degradated by papain. This soluble chitosan had certain antibacterial and preservation effect. The concentration of 1% chitosan solution treatment significantly reduces the carambola decay degree and rate of weight loss,delay fruit storage period of soluble solids,total sugar content and vitamin C reduce,improves the quality of carambola during storage. The activity of 2% chitosan group was the strongest,and suppressed zones of Escherichia coli,Bacillus subtilis,Staphylococcus aureus were(7.821±0.583),(7.399±0.402),(6.439±0.405) mm. The research showed that the soluble chitosan from larva of housefly had good effect on preservation of Carambola and had antibacterial effects