Potato is the main economic and staple food crop in the semiarid loess region of Northwest China. Potato productivity in this area is low because of water shortage and low temperatures in early spring. The use of plastic mulch captures evaporating water, thus suppressing evaporation and maintaining soil moisture. This significantly improves the rainfall-use efficiency, allows the full utilization of light and heat resources, and significantly increases the yield in wheat, corn, and other crops. However, potato plantings covered with transparent plastic film will suffer high temperature stress in the late growth stage, which will restrict further growth and reduce yield. Black plastic film, however, has low transmittance and therefore allows less radiant heat to reach the soil surface. Hence, the soil warming magnitude of black plastic film is smaller than that of the transparent film. This prevents significantly the adverse effects of high temperature on potato and in turn increases potato yield. Potato plantings have been widely mulched with black plastic film by farmers in dryland in the central and eastern parts of the Gansu Province, China. They have also reported the water-saving effects and increased yield in potato that has been mulched with black plastic film. However, systematic studies on the mechanisms of black plastic film mulching that are responsible for the increased potato yield are still lacking. In particular, there is no research on the effects of black plastic film mulching on soil temperature and soil moisture dissipation. Therefore, the aim of this study was to reveal the effects of black film mulching on soil temperature, soil moisture, and potato yield in the semiarid area of Northwest China and to explore the mechanisms responsible for increased crop yield and sustained soil moisture. This study will provide the theoretical support for high yield and high efficiency and contribute to the development of ecologically sound potato cultivation techniques. Potatoes were grown over a four-year period in a randomized block design experiment with two treatments. The two treatments were as follows: 1) whole field surface mulched with black plastic and planting on ridge (PM) and 2) surface uncovered and flat planting (CK). The results showed that the PM treatment increased the average soil temperature by 1.5 ℃ in the top 0-25 cm of soil profile compared to the temperature in the CK treatment. During the flowering stage of the potato, the soil temperature under the PM treatment was increased at 08:00, decreased at 14:00, and stabilized at 20:00 compared to the temperature in the CK treatment. In dry years and years with an average rainfall, PM treatment promoted water consumption during the flowering and tuber expanding stage of potato. PM treatment increased water consumption by 21.2%-50.5% during the flowering stage and by 5.4%-57.9% during the tuber expanding stage, but soil water consumption during the whole growth period was not significantly different between the PM and CK treatments. Because of soil temperature regulation and increased soil water consumption during the critical growth periods, the PM treatment significantly increased potato yield by 13.6%-64.5% and water use efficiency by 24.1%-69.5% compared with the CK treatment. PM treatment increased potato production continuously and increased the soil water stored in the 0-200 cm of the soil by 123.4 mm over 4 years (the average annual rainfall was 391.4 mm). Potato culture with black plastic mulching increased crop productivity and optimized soil water status when compared with control plots.