A cross-linking core-shell structured polyacrylate latex polymer was synthesized by batch seeded emulsion polymerization with methyl methacrylate and butyl acrylate as main monomers, and pentaerythritol triacrylate as a cross-linking agent. FTIR results showed the absorption peak at 3442 cm-1 was attributed to —OH from pentaerythritol triacrylate, and a absorption peak of C O at 1735 cm-1 was obviously enhanced in the modified polymer. TEM photographs indicated that the modified latex particles possess regular core-shell structure. There are great improvements in water resistance, mechanical property and thermal property of the modified latex film. Compared to the film of the unmodified polyacrylate latex, water absorption capacity of modified latex film declines 21. 7% , tensile strength at break increases from 0. 25 MPa to 0. 46 MPa, and elongation at break increase 35. 8% ; 5% , 30% and 50% weight loss temperature of modified latex increase 35 ℃ ,53 ℃ and 88 ℃ respectively.