Abstract: WSi2/MoSi2 composites with different compositions were prepared by in-situ synthesis pressureless sintering using Mo,Si and W powders as raw materials.The effect of the in-situ synthesized WSi2 content on microstructure and mechanical properties of the MoSi2 composite was studied.The results show that the composite consisted of WSi2 and MoSi2 phases which formed as solid-solution,in addition,a few of(MoyW1-y)5Si3 phase was found.Compared with the mono MoSi2,the mechanical properties of the composite improved significantly.The one with 20% WSi2 had the best properties,whose flexural strength at 1 000 ℃ and rooin temperature fracture toughness were 367.3 MPa and 7.87 MPa·m1/2 respectively.The strengthening mechanism of the composite was the second phase particles strengthening and solid solution strengthening ,and toughening mechanism was the second phase particles toughening and crack deflection.