The main objective of the present study was to develop and evaluate a rub threshing machine to suit threshing of sunflower crop, and applies the theory of frictional rubbing and impacting force, and also to evaluate the threshing machine at different factors which affecting the threshing operation such as, (drum speed, impact plates numbers, the clearance between the impact plates and the bottom of the feeding chute “concave clearance" and moisture content). The performance of the threshing machine was evaluated with consideration of the items of the threshing loss, the efficiency of the threshing, the damage of the seeds (visible and invisible), the productivity of the threshing machine, the required power, the energy-specific consumption, and the total cost. The results showed that, the optimum conditions for threshing sunflower by the modified thresher were 10.12 m/s, 24 plates, 2.5 cm, and 11.28% w.b of drum speed, drum knife numbers, and moisture content respectively.