In order to evaluate different nitrogen rates and plant density on yield, morphological traits, protein percent and yield of grain sorghum (Sistan cultivar), an experiment was conducted in split plots based on randomized complete block design with three replications in agricultural research station of Zahak during 2013. The main plots were four nitrogen levels (0, 75, 150 and 225 kg/ha) and sub-plots were four plant density levels (12, 15, 25 and 50 plant/m²). The results showed that plant height, tiller number per plant, stem diameter, length and width of panicle, area of flag leaf, percent and yield of protein and grain yield responded to nitrogen levels and plant density significantly. Also, the interaction of nitrogen and plant density was significant on all traits except plant height and leaf number in main stem. Means comparison showed that by increasing the rate of nitrogen application from 0 to 225 kg/ha, plant height, tiller number per plant, stem diameter, leaf number per main stem, length and width of panicle increased, 8.9, 45.6, 67.1, 10.3, 58.6 and 117%, respectively and area of flag leaf, protein and grain yield increased, 2.13, 3.21 and 4.3 times, respectively. In addition, the results indicated that by increasing in plant density from 12 to 50 plant/m² plant height and grain and protein yield increased 23.5, 76.7 and 69.4%, respectively but tiller number per plant, stem diameter, length and width of panicle, flag leaf and protein and grain yield decreased, 62.9, 37.5, 20.7, 23.6 and 32.5%, respectively. Totally, according to the present study results, 225 kg/ha nitrogen fertilizer application and 50 plant/m² treatment are recommended for grain sorghum Sistan cultivar cultivation in Zabol region because of the maximum grain yield and protein in unit area.