Abstarct: In this research, in order to estimate the effect of split application of nitrogen on yield and yield component of corn a field experiment was carried out in research farm of Agricultural college, Shahrood University of Technology, Iran (2007). Split plot experiments on the basis of randomized, complete block design with four replications were conducted. In this study three varieties of corn (C1=370, C2= 447, C3=499) were placed in main plots and split application of nitrogen (N1=98Kg Urea/ha in planting time, 294Kg Urea/ha in flowering time, N2=196Kg Urea/ha in planting time, 196Kg Urea/ha in flowering time, N3=294Kg Urea/ha in planting time, 98Kg Urea/ha in flowering time, N4=98Kg Urea/ha in planting time, 147Kg Urea/ha three weeks before flowering, 147Kg Urea/ha three weeks later flowering, N5=196Kg Urea/ha in planting time, 98 Kg Urea/ha three weeks before flowering, 98Kg Urea/ha three weeks later flowering, N6=294Kg Urea/ha in planting time, 49Kg Urea/ha three weeks before flowering, 49Kg Urea/ha three weeks later flowering) were placed in sub plots. Obtained results show that corn varieties had a significant difference for on yield. The highest yield was recorded by third variety (C3). Also varieties have a significant effect on kernel weight per bush, number of ear, kernel number per row, kernel number per ear, ear weight, corncob weight, harvest index and high bush. The field tests reveal that split application of nitrogen had significant effect on yield too. Split application with N4 pattern (98:147:147) was the preferred treatment due to 8/026 Ton/ha increment to other treatments. Also mean difference of kernel weight per bush, number of ear, number of row per ear, number of kernel per row, 100 grain weight, number of kernel per ear, ear weight, corncob weight, spath weight, harvest index, biologic yield, high bush and Stover diameter had significant effect under split application of nitrogen fertilizer. also the results reveal that interaction effects of three varieties of maize and split application urea in different times have significant effect on the yield, kernel weight per bush, number of ear, number of rows per ear, number of kernel per row, number of kernel per ear, ear weight, corncob weight, spath weight and harvest index.The results of growth analysis showed that the process of TDM, LAI, CGR, RGR, NAR dependant on varieties and split application of nitrogen. In other to the third variety (C3) with (N1) pattern are suggested in Shahrood.