Maleic acid polyether ester(Ester-61) was synthesized from polyether glycol(L61) and maleic anhydride(MA) with p-toluenesulfonic acid as the catalyst. The reaction conditions were studied by orthogonal experiment. The results showed that the optimum reaction conditions were as follows, the mass ratio of L61 to MA was1.5:1, the content of p-toluenesulfonic acid was 1.8%, the reaction temperature was 150℃ and the reaction time was 8 h. A novel comb-like bicomper(DEMU-L61)with hydrophilic side chains was synthesized from Ester-61 and allyl polyethylene glycol(XPEG-1000) using benzoyl peroxide(BPO) as the initiator by free radical solution copolymerization when the mass ratio of Ester-L61 to XPEG-1000 was 1:0.9, the content of BPO was 1.0%, reaction temperature was 120℃ and reaction time was5 h. IR and NMR analysis showed the synthesized product was a target product. The DEMU-L61, obtained under the optimum conditions, had a good performance in the demulsification of crude oil from Yanchang oilfield Eastern district, the demulsification rate being about 99%, the purification oil content being less than 0.5% water.