【Objective】 This study was conducted to investigate spatial variation of the effect of soil-testing-based-formulated-fertilization of wheat, as compared with conventional fertilization, in an attempt to provide a scientific basis for adjusting technical parameters and optimizing fertilizer formula specifically for a farmland. 【Method】 Data were collected from 296 field experiment sites set for demonstration of soil-testing-based-formulated-fertilization (STBFF) of wheat in Nanyang city for analysis and evaluation of effects of STBFF on yield and income of wheat at various locations as compared with conventional fertilization, based on spatialized estimation of fertilization rate and modeling of geographically weighted regression (GWR) for relationship between wheat yield and fertilization rate. The spatial variation of the effect of STBFF of wheat, embodied by increment in wheat yield and income, was evaluated on the basis of the prediction of wheat yield and analysis of its spatial distribution pattern. 【Result】 The spatial distribution pattern of wheat yield of the STBFF was similar to that of the conventional fertilization. The wheat yield was increased from 5 970 kg?hm^-2 to 6 672 kg?hm^-2, when conventional fertilization was converted into STBFF, with an average increment of wheat yield being 11.76% (the increment varied with the county in the range of 7.04% ~ 17.91%) and an average increment of income being 1 232 Yuan?hm^-2 (the increment varied with the county in the range of 713 Yuan?hm^-2 ~ 1 672 Yuan?hm^-2). 【Conclusion】 Spatial variation of the effects was quite obvious. The regions enjoying high increments of wheat yield and income were distributed mainly in Nanzhao, Xixia, Zhenping, Xinye and Sheqi counties, however, some regions in Neixiang, Tanghe and Tongbai counties suffered negative effects. Although STBFF can improve generally yield of the wheat in Nanyang city, the spatial distribution pattern of wheat yield in this area is affected by some factors like physical conditions, soil conditions and agricultural management level of a region.