The invention discloses a natural polymer film material with an adjustable degradation rate and a preparation method, which belongs to the technical field of environmentally-friendly polymer film materials. The natural polymer film material comprises the following components in percentage by mass: 5 to 55 percent of water, 35 to 50 percent of natural starch, 5 to 30 percent of konjac fine flour, 5 to 10 percent of lactic acid, 0.1 to 5 percent of glycerin, and 0.001 to 1 percent of tackifier prepared from ammonia water and ethanol. Rich food-grade natural polymer materials, such as the natural starch, the konjac fine flour and the like, form a main raw material source, so the film material does not damage a human body, and can be completely degraded under natural conditions. Process parameters in a process comprising mixing, microwave treatment, curtain coating and sizing are adjusted to realize regulation and control over the degradation rate of the film material, greatly reduce the viscosity of glue solution, expand the viscosity range of the glue solution, reduce the processing cost of the film and avoid detriments to the environment. The film can be widely applied to packaging, food preservation, beauty masks, agricultural mulching films, medical consumables, hygienic products, biochemical isolation or dialysis, and the like.