Abstract: Compound freshness keeping coating agent was mainly made of konjac glucomannan, chitosan and emulsifier. In order to investigate the effect of the coating agent on Longan storaged at room temperature, the optimum coating prescription(containing a certain restraining mold reagent) was obtained by orthogonal experiment. The concentrations of konjac glucomannan, chitosan and sucrose ester of fatty acid are 0.2%, 0.2% and 0.15% respectively. Further experimental results show that such coating agent can effectively enhance the rate of healthy fruit during storage and the rate of Longon healthy fruit is 82% after seven days storage at room temperature. The microscopical photographs indicate that the compound coating agent can form a white compact semi-transparent film on Longan pericarp and then permeate through the micro-hole of external pericarp, which cover the pores on Longan pericarp surface.