This study was to develop the time-specific and time-critical method to overcome the limitations of traditional field sampling methods for variable rate fertilization. Farmers, agricultural managers and grain processing enterprises are interested in measuring and assessing soil and crop status in order to apply adequate fertilizer quantities to crop growth. This paper focused on studying the relationship between vegetation index (OSAVI) and nitrogen content to determine the amount of nitrogen fertilizer recommended for variable rate management in precision agriculture. The uniform rate fertilizer management was chosen as the CK. Analyses revealed that the red edge of the wheat canopy reflectance spectrum had distinct “red shift” and increased red peak in variable-rate zones. The variable-rate nitrogen fertilization reduced the variability of wheat yield and OSAVI and increased wheat yield, compared to uniform rate fertilizer application. There was a big difference for canopy spectral reflectance between two nitrogen application types in wavebands of 670nm and 760-900nm at elongation stage.