In this paper Mengjin County of Henan Province we selected as the study area, slowly available K contained in topsoil was spatially predicated by the method of spatial regression analysis with the terrain characteristics, included slope, elevation, curvature and CTI. The results indicated that the slowly available K had a distance threshold of spatial autocorrelation around 10 000 m and a significant correlation between slope, elevation, curvature and soil available K. Although output precision of the spatial regression model was quite similar to that of the classic regression ones, the spatial regression model displayed an evident advantage to reveal further the spatial distribution pattern and variation characteristics of soil property.