In order to study of variation and relationships between morphological traits with yield and its components in three grain sorghum cultivars (Kimia, Sepideh and Payam) and nine promising lines (Mgs1-Mgs9) received from Seed and Plant Improvement Institute, an experiment was conducted as randomized complete block design with four replications in Birjand agricultural research station, in two growing season. Morphological traits including plant height stem diameter, flag leaf area, panicle length, tiller number, number of seeds per panicle, 1000-kernel weight, harvest index and grain yield were measured. According to results of Combined Analysis, investigated cultivars and lines were significantly different at 1% probability level about majority of traits that indicate there is high variation between studied lines and cultivars. According to path analysis, dry weight of panicle had the highest direct effect on grain yield. while number of seeds per panicle, 1000-kernel weight and panicle length had indirect effect on grain yield via dry weight of panicle. Thus, such traits should be considered in yield breeding program together. Also tiller number had the highest negative indirect effect on grain yield, so in order to acces to lines with high yield, lines with lower tiller number should be selected.