In this study, through geostatistics analysis and grey relation analysis, the relationship between environmental factors and spatial autocorrelation patterns of topsoil SOM in Baojiagou watershed of feldspathic sandstone region was studied. The results showed that spherical model was appropriate to evaluate the spatial distribution of topsoil SOM of small watershed in soft sandstone area, the values of nugget-to-sill were 60.66%, and the spatial autocorrelation of topsoil SOM was at moderate level, it was also found that topsoil SOM content according to topographic factors was in a trend of valley floor>slope> ridge. Global spatial autocorrelation showed that topsoil SOM had an obvious characteristic of positive autocorrelation, the local spatial autocorrelation mainly displayed a high with high correlation and low with low correlation types, and few high with low value agglomeration. The H-H agglomeration was mainly distributed in the valley and forest in the middle of watershed, the L-L agglomeration mainly in the bare slope in the downside of watershed, and the anomalous zone in the grass slope in the upside and downside of watershed. The results of grey correlative degree analysis showed that topographic wetness index (TWI) had the most significant influence on H-H agglomeration, slope position had the strongest correlation with L-L agglomeration, with associated degree 0.489, land use type was the important factor influencing the anomalous zone of H-L agglomeration. In conclusion, topographic factors are the leading factors for the formation of high value accumulation areas of topsoil SOM in small watershed of feldspathic sandstone area, while land use type can interfere with the formation of high/low value accumulation areas of topsoil SOM.