The reactive Gibbs free energies, the reactive formation enthalpies and adiabatic temperatures concerning the preparation ofMoSi2-WSi2 composites using elemental powders of Mo, W and Si by the thermal explosion mode of SHS have been theoreticallycalculated and investigated by experiments. XRD, SEM and EDAX have analyzed the phase compositions and micro-area chemicalanalyses of the products. The results show that the reactive formation enthalpies of MoSi2 and WSi2 are biggest, 234.645 kJ/mol and195.670 kJ/mol respectively, when the reactions take place at 1685 K (the melting point of Si). And when the initial temperature is 1685 Kthe products of all systems have fused completely. Pure MoSi2-WSi2 composites are fabricated by the thermal explosion mode of SHS, andMoSi2-WSi2 exists as solid solution of (Mox,W1-x)Si2 while the chemical elements of every grain are not uniform.