The invention provides a preparation method of a curcumin rare earth complex, a composite heat stabilizer for rigid PVC (polyvinyl chloride) and a preparation method of the composite heat stabilizer. The preparation method of the curcumin rare earth complex comprises steps as follows: curcumin and absolute ethyl alcohol are added to a flask and heated until curcumin is dissolved completely; a rare earth nitrate solution is dropwise added to the flask, and the pH value is regulated to 6.0 plus or minus 0.2; the mixture is continuously stirred and flows back, after the reaction is finished, the mixture is cooled to the room temperature and is subjected to extraction filtration, precipitates obtained through extraction filtration are washed with absolute ethyl alcohol and subjected to extraction filtration and vacuum drying, and the curcumin rare earth complex is obtained. The composite heat stabilizer for rigid PVC comprises components in parts by weight as follows: 100 parts of the curcumin rare earth complex, 0-20 parts of an antioxidant 1010, 5-20 parts of glyceryl monostearate, 5-20 parts of glyceryl tristearate, 15-50 parts of calcium stearate and 5-10 parts of zinc stearate. The composite heat stabilizer for rigid PVC has excellent heat stabilizing effect on processing of a PVC product, and meanwhile, the PVC product has excellent rheological properties and mechanical properties.