The invention provides a degradation method for polyvinyl chloride plastics. The degradation method comprises the following concrete steps: S1, screening and cleaning collected plastic raw materials,and carrying out mechanical damage to reduce the volume of the raw materials; S2, soaking the pretreated raw materials in a soaking solution for 24-72 hours and maintaining a soaking temperature to be37-60 DEG C; S3, washing the soaked raw materials and adding the soaked raw materials into a fermentation tank for fermentation and degradation; and S4, collecting degraded mixed liquid for secondaryextraction and recycling. The method of the invention allows the plastics to be conveniently and repeatedly recycled; after the waste plastics are recycled, the recycled plastics can be made into products again and can also be used for preparing gasoline and diesel oil; so environmental and social problems brought by plastic pollution can be effectively solved.