Belonging to the technical field of foam materials, the invention provides a fine-pore polyvinyl chloride foam material and a preparation method thereof. The invention solves the technical problems oflarge and uneven cells of cross-linked rigid polyvinyl chloride foams, easy degradation and gelatinization of plate core, and long steam curing time and low efficiency of preparation method in the prior art. The foam material provided by the invention comprises 100 parts by weight of polyvinyl chloride resin, 0-80 parts by weight of anhydride, 0-20 parts by weight of an epoxy compound, 30-150 parts by weight of isocyanate, 5-20 parts by weight of a foaming agent 1, 0-5 parts by weight of a foaming agent 2, 2-20 parts by weight of a foaming agent 3, 0-4 parts by weight of a catalyst, 0-3 partsby weight of a surfactant and 5-20 parts by weight of a thermal stabilizer, and the cell diameter of the foam material is 300microm-100microm. The foam material can reduce the cell diameter of foam material, lower the absorption of resin in a composite material preparation process, reduce the product weight, and avoid plate core degradation and gelatinization.