Abstract: A combined method with geostatistics and GIS was applied to analyze the characteristics of spatial variability of total nitrogen (TN) in topsoil and their affecting factors in Zhangdigou small watershed in Shangzhou District. The results showed that mean TN content in topsoil were 0.986g/kg, and its coefficient of variation was 24.14% falling into moderate variation. TN content in topsoil occurred high spatial autocorrelation mainly caused by structural factors. The spatial distribution of TN content in topsoil exhibited patch-shaped and ribbon-shaped patterns. TN content in topsoil decreased in the order of farm land, orchard, woodland and grassland. TN content,changed significantly with elevation, diminishing with increased elevation and slope. The highest value of TN content was in sunny slope while lowest in semi-shady slope. The conclusion could provide scientific proof for agriculture structure adjustment, effective utilization of total nitrogen and improvement of water quality in Danjiang watershed.