The invention relates to an organic tin composite stabilizing agent for preparing PVC and a preparation method of the stabilizing agent. The organic tin composite stabilizing agent is prepared from, by weight, 40-60 parts of organic tin, 10-20 parts of organic metal sodium salt, 10-20 parts of organic metal potassium salt, 5-20 parts of a lubricant, 5-10 parts of phosphite, 1-5 parts of an epoxy compound and 1-5 parts of an auxiliary heat stabilizer. The invention further provides the method for preparing the organic tin composite stabilizing agent. The organic tin composite stabilizing agent for preparing the PVC can be applied to the processing fields of PCV of sheets, soft product transparent films and the like, the cost is lower compared with organic tin, the lubricity is better compared with organic tin, and the processing property is excellent.