Abstract: The sweet potato is one of the most important crops in China, and the plastic film mulch was an important agronomic practice increasing the yield of sweet potato, this article reviewed the yield-increasing mechanism of plastic film mulch which mainly lay in the following aspects. The first was that the plastic film mulch increased the temperature and humidity of soil, improved the physical and chemical properties and accelerated the conversion of nutrient in soil. The second was that the plastic film mulch made tuber formation earlier than that of bare ground and improved the development of root and prevented the over growth of leaves and stems. The third was that the plastic film mulch increased the content of chlorophyll and the activity of Rubpase, ATP, SOD and CAT and decreased the content of MDA in leaves, which increased the photosynthetic rate delayed the senescence of leaf, and the plastic film mulch changed the trends of phytohormone content in leaf and tuber root which improved the assimilate transports from leaf to tuber root. The last was that the plastic film mulch increased the ability against insects and pathogens and the stress of saline. And then the problems of plastic film mulch such as the environmental pollution, production reduction and incompatibility between agricultural machinery and agriculture existed in sweet potato production, meanwhile the trends of plastic film mulch was discussed.