In order to explore in depth intrinsic mechanism of using nuclide tracer technique to study soil erosion deeply, spatial heterogeneity and distribution of ¹³⁷Cs & ²¹⁰Pb_ex in a slope in Ningzhen region were studied with the geostatistics method based on the module of Arcgis Geostatistics. Results shows that the unique physicochemical properties of ¹³⁷Cs & ²¹⁰Pb_ex make them distinct from others in spatial heterogeneity and distribution characteristics in slope. The biggish Nugget of ¹³⁷Cs & ²¹⁰Pb_ex indicates that their spatial distribution is definitively influenced by random factors such as soil erosion, farming practices, etc. And it is why they can be used to trace soil erosion. The medium degree of spatial autocorrelation and distribution patterns of ¹³⁷Cs on slope reflect preferably that landform as a structural factor can influence its spatial distribution. Results of the tracing of soil erosion using ¹³⁷Cs should be more comprehensive, more reasonable, and more macroscopical. The very week spatial autocorrelation of ²¹⁰Pb_ex explain that its spatial distribution is more sensitive to the influence of random factors. And it is better at exposing details of soil erosion.. The distribution patterns on a slope differ quite much between ¹³⁷Cs & ²¹⁰Pb_ex, which, on the one hand, indicates that they differ from each other quite sharply in their initial sedimentation layout, partial physicochemical properties, and responses to various affecting factors for variation, etc. and on the other hand, it also hints that the courses of soil erosion traced with ¹³⁷Cs and ²¹⁰Pb_ex can hardly reach an agreement even through adjustment of their calculation models.