In this paper,potato starch,polyethylene glycol were used as the raw materials,adopting trans- glycosylation to synthesize polyethylene glycol glycoside,with the yield of the target product as the research index,the optimum conditions of synthesizing polyethylene glycol glycoside were investigated by orthogonal as follows: reaction temperature 118℃, reaction time 4.5h, m(starch):m(PTSA): m(ethylene glycol):m(PEG800)=1:0.025:4:2.The yield of the target product was 154.58%.The product was characterized with FT-IR, GC-MS and the moisture retention was analyzed. The results showed that the product belong to a kind of glycosidic substances, and the product with excellent moisture retentiveness was obtained.