Influence of air void content of polyacrylic ester latex(VIVID400), polyvinyl acetate ethylene latex(CP149) and styrene butadiene latex(SD623) modified cement mortar was investigated with fixed flow value. The research shows that bulk density of fresh mortar decreases due to air entrainment of polymer latex, but increases with increasing dosage of defoamer to varying degrees. The flexural strength and compressive strength of polymerized mortar increase with the increasing of dosage of deformer. The tensile bond strength of VIVID400 modified mortar increases at first, then decreases with the lower air void content, probably because of the influence of the defoamer on the micro pore structure of the mortar.