The invention provides a plain area soil organic carbon three-dimensional space distribution simulation method. The method comprises the steps of (1) fitting a soil organic carbon profile change optimal depth function and determining function parameters; (2) analyzing influence factors of soil organic carbon profile depth function parameters; and (3) constructing and calculating a three-dimensional space distribution simulation model. According to the invention, environment auxiliary variables for simulating soil property spatial distribution in a smooth terrain area are constructed; a soil depth transfer function and a regression Kriging method are used to establish a soil organic carbon three-dimensional space distribution simulation model in the smooth terrain area; the three-dimensional space distribution simulation method research of the soil organic carbon in the region is carried out; a reliable simulation method can be provided for accurately mastering soil organic carbon three-dimensional space-time evolution information under the high-strength agricultural utilization background of the terrain smooth area, and a method reference can be provided for accurately estimating the organic carbon reserve of the area and guaranteeing the soil safety and the grain safety.