P(VP-co-BA-co-CA) polymer surfactant was obtained from N-vinyl-2-pyrrolidone(VP),butyl acrylate (BA),carboxyethyl-2-methacrylate(CA) by solution polymerization.And the water-dispersible 1, 6-diisocyanate (HDI) trimer(abbreviated as WD-HDIT) was prepared from 1,6-diisocyanate(HDI) trimer and P(VP-co-BA-co-CA), which used as an emulsifier. The surface sizing properties of WD-HDIT emulsion were discussed and the synthetic condition were also optimized. The results showed that the emulsion presents excellent stability and outstanding sizing properties when w(VP) was 5.0%,w(BA) was 3.4%,w(CA) was1.3%，w(HDI) was 60.0%.Paper sizing value could reach 29 s,the water contact angle was 119.49°, the folding endurance could approach 67 times, the paper tensile strength was 55.8N·m/g, the bending stiffness was 2.003 N•m7/kg3, the ring crush strength was 5.1468N•m/g when the dosage of the sizing agent was 10%.