The thermodynamic calculation was used to evaluate the possible temperature range for preparing the Mo4.8Si3C0.6 powders by a solid reaction method using molybdenum，silicon and carbon powder as the main raw materials. Influence of temperature on composition，specific surface area，size and microstructure of the obtained materials was investigated by using the X-ray diffraction （XRD），scanning electron microscopy （SEM），BET，et al. The results show that the standard Gibbs free energy for the formation of Mo4.8Si3C0.6 is only -351.3 ~ -338.1 kJ/mol when the temperature range is between 1 400 ~1 900 K. Experimental results show that when the temperature keeps at 1 823 K for 1.5 h，the obtained Mo4.8Si3C0.6 powder possesses high purity，petal-liked shape with a diameter about 4.5 μm，specific surface area of 0.753 3 m2/g and particle size of about 1.23 μm. The reaction mechanism for the formation of Mo4.8Si3C0.6 powder is that，when the reaction temperature keeps at 1 373 K，the main product is Mo2C; when it reaches 1 523 K，the main product is Mo5Si3，and a small amount of Mo4.8Si3C0.6；when it rises to 1 673 K，the main product is Mo4.8Si3C0.6，and minor Mo5Si3；finally，when the temperature reaches 1 823 K，no impurities phase of Mo4.8Si3C0.6 is obtained.