Determination of unit plot is very important for soil loss prediction, it is also a key base to researches on erosion mechanism. According to environmental conditions, characteristics of soil erosion and agricultural production, standard of unit plot in China was studied based on analysis of landform features of erosive regions, previous data from field observation, and error diffusion in soil loss prediction. The Standard of Unit Plot in Soil Loss Prediction of China was put forward, the unit plot is 20 m long, 5 m wide, with a uniform length-wise slope of 15°, in continuous fallow and preparation in accordance with local farming system.