A rare earth compound thermal stabilizer for PVC and a preparation method therefor. The rare earth compound thermal stabilizer comprises the following components in parts by weight : 10-70 parts of rare earth salt; 3-70 parts of zinc stearate; 1-15 parts of an antioxidant; 1-10 parts of zeolite; 1-10 parts of calcium perchlorate; 0-10 parts of mixed fatty acid; 1-5 parts of naphthenic acid, 5-20 parts of epoxy fatty acid, 10-15 parts of paraffin, 1-3 parts of trimethylolpropane, 2-4 parts of sorbitol, and 3.5-20 parts of diisononyl phthalate. The rare earth compound thermal stabilizer is the environment-friendly, highly stable and cheap stabilizer.