This study was carried out at the Experimental Farm, Faculty of Agriculture, Sohag University, Sohag, Egypt during two successive winter seasons 2010/2011 and 2011/2012 to investigate the effect of nitrogen and potassium fertilization on onion seed production Improved Giza 6 cultivar. Three nitrogen rates (50, 100 and 150 kg feddan , one feddan= 0.42 ha) and three potassium rates (40, 80 and 120 kg feddan ) were 11 used in this study. The new Duncan’s multiple range tests showed that the nitrogen fertilizer doses had significant effect on all traits. Moreover, potassium fertilizer rates significantly affected on seed yield parameters, except umbel diameter. The maximum seed yield feddan was obtained by the high nitrogen rates 1 and the medium potassium rates. Seed yield plant and feddan were influenced by days to sprout, plant 11 height, number of leaves plant , number of stalks plant , days to flowering, flower stalks height and weight 11 of seeds umbel .