To evaluate the effects of nitrogen management at yellow budding stage on seed yield with using nitrogen nutrition index (ratio of nitrogen concentration in the plant to optimum concentration), of rapeseed farms in Gorgan, an experiment was conducted as a nested model arranged in a complete randomized design (CRD) in 2010. Fifteen rapeseed fields were classified at three levels of management (optimum, middle, weak). During the experiment, questionnaires were completed by farmers for quantification of agricultural management. The results showed that levels of management are significantly difference from nitrogen nutrition index (NNI) (P<0.01). Although quantities of nitrogen nutrition index (NNI) were higher in optimum level of management than the middle and weak levels, but at all management levels during the growing season, the index was less than one. This indicates restriction in development and production due to nitrogen deficiency. Nitrogen nutrition index in yellow budding stage have, significant positive correlation (P<0.05) with seed yield, and confirmed importance of access to nitrogen sources in yellow budding stage.