An apparatus developed for measurement of dynamic friction coefficient is presented. The dynamic friction coefficient of paddy grains was determined and studied in three varieties (Alikazemy, Hashemi and Khazar), at two levels of moisture content (12 and 23% w.b.), three levels of peripheral speed (0.5, 3.5 and 6.5 cm s-1) and on three contact surfaces (black, mild and galvanized sheets). The experiments were arranged as a split-split plot fitted into randomized complete block. The results of variance analysis revealed that the effects of grain moisture content, variety, contact surface, peripheral speed and their interactions were significant (p<0.01) on dynamic friction coefficient. With increase in the moisture content of grain and peripheral speed of disc, dynamic friction coefficient increased. Among the contact surfaces, the highest and lowest values of dynamic friction coefficient were 0.567 and 0.314 and belonged to the black and galvanized sheets, respectively. Also, among the varieties, Alikazemi and Khazar varieties had the maximum and minimum mean values, respectively.