Abstract: DSC,DMA and SEM were used to characterize melt and crystallization behavior,morphology and compatibility of ternary blends,at the same time,tensile properties of ternary blends were investigated.The results show that the content of HIPS-g-GMA is less than 15 phr,size of domains get smaller and particle dispersion is more uniform.In addition,two T_g relaxation peaks of ternary blends response to T_g of PS and T_g of PBT,which shift to lower temperature;mechanical properties of ternary blends were improved.Smaller size of domains,lower T_g temperature,higher mechanical properties resulted from(interaction) of epoxy group of HIPS-g-GMA and carboxyl group and/or hydroxyl group of PBT,it made(adhesion) of PBT and HIPS get strong.