Abstract: The strengthening-toughening effect and mechanism of SiC whiskers and Si3N4 particles on MoSi2 matrix were premilimary investigated and discussed through the observation of microstructure and the measurement of mechanical properties.The results show that the bending strength,Vickers-hardness and fracture toughness of the composite were improved obviously due to the addition of SiC whiskers and Si3N4 particles.The strengthening mechanism of the composite was the effect of dispersion strengthening and grain refining.The bending strength reached 427 MPa.The toughening mechanism was the synthetic effect of grain refining,crack deflection and crack branching.The room temperature fracture toughness of Si3N4p-SiCw/MoSi2 composite was 10.4 MPa·m1/2.