With the aim to provide scientific and guidance for the sustainable development of Weibei Tableland cultivated land, a study was conducted to explore the application of Cokriging with OM as auxiliary variable in the regional spatial estimation of topsoil TN content and carbon to nitrogen ratio (C/N) applying traditional statistics, geostatistics combining with GIS technology. The spatial variability and influencing factors of topsoil OM and TN was researched and the spatial pattern of their contents and topsoil C/N was further analyzed based on the data of the Cultivated Land Productivity Investigation and Quality Evaluation Project of Pucheng County in 2011. The results showed that the current average content of topsoil OM was 13.58g/kg, TN was 0.81g/kg and C/N was 9.84, and all of them were in relatively low level. Spatially, topsoil OM and TN contents generally increased from north to south along with geomorphologic types while topsoil C/N was high in north and south and low in the middle. Both OM and TN showed spatial cluster at 0.01 significance level and demonstrated moderate spatial correlation. The spatial variability was influenced by both natural factors such as topography and geomorphology, soil types and human factors including fertilization, cropping system, irrigation and so on, and the geographical guide of human activity was playing more and more important roles. With the same sampling numbers (n=554), compared with ordinary Kriging, Cokriging with OM as subsidiary variable was more suitable for spatial interpolation of TN and could provide more local variation information, but was unavailable for the raster ratio calculation to obtain soil C/N map.