The effect of VAE latex modification on the physical properties of cement mortar is investigated. The porosity problem in cement mortar modified by vinyl acetate ester-ethylene (VAE) copolymer emulsion was successfully resolved by reasonable defoaming technique. It is shown that the bond strength and water resistance properties of modified cement mortar are better than unmodified cement mortar. When polymer-cement ratios ranged from 0 to 0.25, the bond strength and anti-permeability increased first and then decreased. The best value appeared at 0.1(polymer-cement ratio). SEM shows that the modified sample has compacted structure, polymeric films wrap the cement body and fill in the gap between cement and sand to improve the interfacial bond.