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The mechanical properties of MoSi2 based composites containing various types of reinforcement, such as SiC, ZrO2, and W, were investigated, based on detailed examinations of their microstructures. MoSi2 based composites were fabricated at a temperature of 1350℃ using a hot-press device. The volume fraction of SiC and ZrO2 particles in this composite system was fixed as 20%. The volume fraction of three types of W particles was changed from 10% to 30%. The characteristics of the MoSi2 based composites were determined by means of optical microscopy and a three-point bending test. The addition of W particles to the MoSi2 powders exhibited a sufficient improvement in the microstructure and mechanical property of the sintered MoSi2 materials, compared to those of SiC and ZrO2 particles. In particular, W/MoSi2 composites containing W particles of 20 vol% represented a good flexural strength of about 530MPa at room temperature, accompanying a relative density of about 92%. The flexural strength of the W/MoSi2 composites tended to decrease with an increase in the average size of the W particles.