Abstract: Effect of block copolymer of styrene and butadiene (SBS), maleic anhydride grafted SBS (MAH-SBS) and nano-CaCO₃ on PC-ABS blends properties were studied, and the micro structure was observed by SEM. It is found that when PC:ABS=1:1, the comprehensive properties of PC-ABS is the best; only 4wt% nano-CaCO₃ is added, the tensile strength of nano-CaCO₃/PC-ABS is increased obviously but the impact strength is increased slightly. It is invalid when SBS is used alone. If MAH-SBS is used alone, the impact strength of MAH-SBS/PC-ABS is increased but the tensile strength is decreased seriously. The mixture of MAH-SBS and nano-CaCO₃ have a synergistic effect, the impact strength is increased from 80 kJ/m² to about 108 kJ/m² and the tensile strength is improved from 57.0 MPa to about 61.5 MPa.