The invention discloses a porous carbon preform for reactive sintering, as well as a preparation method and application thereof. The porous carbon preform is obtained by taking charcoal powder as a carbon source, taking lignocellulose as a pore-forming agent, taking a modified polyester type high molecular compound as a dispersant, taking camphene as a dispersion medium, adding a certain amount of ethyl ether, performing constant-temperature ball milling at the temperature of 55 DEG C to obtain material slurry, performing vacuum degassing, then pouring and forming the material slurry at room temperature, subliming till constant weight, and carrying out biscuit firing at the temperature of 900-1550 DEG C for 0.5-2h. The porous carbon preform prepared by the method disclosed by the invention has the advantages of controllable density and porosity, uniform pore structure, no defects and the like, and has great reactive sintering performance; reaction sintered silicon carbide generated by high-temperature silicon impregnation reaction has no black cores, cracking, delamination and other defects, and has good mechanical properties.