The　self-propagating　high-temperature　synthesis　(SHS)　process　of　a　Ti-C　reactive　system　was　numerically　simulated　to　investigate　the　effect　of　porosity　and　diluent　on　the　SHS　reaction　and　its　activating　mechanism　using　an　implicit　difference　method,　enthalpy-temperature　method　and　the　Gauss-Seidel　iteration　procedure.　The　new　features　of　the　model　include　the　consideration　of　the　melting　of　each　constituent　of　the　reactants　and　product　and　the　inclusion　of　considerations　involving　dilution　and　porosity.　The　simulation　results　indicate　that　as　the　porosity　is　varied,　there　is　not　a　significant　effect　on　the　combustion　temperature　or　mode　of　combustion　front,　and　the　nature　of　the　combustion　front　is　steady　and　uniform　because　of　the　lower　activation　energy　in　the　system.　As　the　porosity　in　the　reactant　decreases,　the　combustion　velocity　first　increases　because　of　the　increase　of　the　thermal　conductivity.　The　combustion　velocity,　after　reaching　a　maximum,　decreases　with　the　further　decrease　of　the　porosity　of　reactant　because　of　the　high　thermal　conductivity　of　the　reactants.　To　study　of　the　effect　of　the　diluent,　the　product　itself　was　considered　as　the　diluent.　Adding　the　diluent　to　the　initial　reactants　decreases　the　combustion　temperature　and　the　combustion　velocity.