Conductive liquid silicone rubber-based composites were prepared through incorporation of fumed silica (FSiO2) and polydimethylsiloxanes (PDMS) modified MWCNTs (P-MWCNTs), and their mechanical and electrical properties were investigated. It is shown that the introduction of P-MWCNTs with P-MWCNTs/FSiO2 ratio of 0.25/30 (w/w) increases the cross-linking density and the thermal stability of the composites significantly. The improved mechanical performance, e.g., 60% increase for Young's modulus and 47% increase for tear strength, should be ascribed to the stronger interfacial interaction between P-MWCNTs and PDMS matrix and better dispersion of P-MWCNTs due to existence of PDMS on CNT surface. Moreover, the better dispersion of P-MWCNTs also ensures much higher electrical conductivity than original carboxyl functionalized MWCNTs (COOH-MWCNTs) at relatively low loading, e.g., 10−3 S m−1 versus 10−8 S m−1 at MWCNTs/FSiO2 ratio of 2.5/30, which could be attributed to the formation of CNT network.