The shortage of oil resources and the need to reduce the environmental burden caused by petroleum-based polymers have driven the development and production of biodegradable materials. In recent decades, natural polymers have replaced current synthetic polymers due to their non-toxicity, biodegradability, and biocompatibility. Starch has been extensively studied for the manufacture of biodegradable composites due to its reproducibility, biodegradability, low cost, and availability, which has been widely used for applications in agriculture, alimentary, medicine and packaging industry. However, the polyhydroxyl structure of starch gives it strong hydrophilicity, and the moisture sensitivity limits their mechanical properties and affects their application. In this paper, mainly from the perspective of improving the physical and chemical effects of thermoplastic starch, the research works in recent years on improving the water resistance of thermoplastic starch material and reducing its sensitivity to environmental humidity are summarized. The related factors affecting the water resistance and the methods of improvement are introduced, and the research trend in this field is also proposed.