Abstract: Nano-CaCO3 filled styrene-butadiene rubber (SBR) powder P(SBR/CaCO3) was prepared with condensation coprecipitation method. The effect of nano-CaCO3 filling amount on the mechanical properties of P(SBR/CaCO3) vulcanizate was studied. Then the material was compared with the bulk vulcanizate of mixed SBR/nano-CaCO3. It is found that when the nano-CaCO3 filling amount of P(SBR/CaCO3) vulcanizate and SBR/CaCO3 vulcanizate was the same, the mechanical properties of the former were basically superior to the later. When the filling amount of the nano-CaCO3 was 100 phr, the best mechanical properties of P(SBR/CaCO3) vulcanizate could be obtained, while the tensile strength could reach 13.38 MPa which was obviously better than that of the SBR/CaCO3 one. It was originate from that the nano-CaCO3 in the former had better dispersion and interface bonding force than that in the later, which led to the better mechanical properties.