The invention belongs to the technical field of porous materials and particularly relates to a method for preparing a porous carbon material of a three-dimensional macro self-support structure. The method includes the steps that a polyvinylpyrrolidone (PVP) solution is prepared, a vacuum lyophilization method is adopted, and a PVP precursor of a porous structure is obtained; then, the precursor is stabilized for 12-48 hours at the constant temperature of 150-200 DEG C, high-temperature carbonization at the temperature of 600-1,000 DEG C is conducted, and porous carbon is obtained; finally, KOH and the porous carbon are mixed in a certain mass proportion, activation is conducted for 1-2 hours at the temperature of 8,000 DEG C, and the porous carbon material integrating micropores, mesopores and macropores is obtained. The method for preparing the porous carbon material is further optimized, the preparation process is easy to operate, the yield is high, the method is environmentally friendly and free of pollution, the pore structure of the prepared porous carbon material is orderly, a high specific surface area is achieved, and the porosity is as high as 90%.