A threshing machine was fabricated and tested to suit the shape and proprieties of sunflower crop. It consisted of a threshing, power drive and power transmission units. Three levels of drum speeds (, 10.9, 8.3 14.7 m/s), three levels of cylinder concave clearance (2, 3, 4cm), three positions of threshing drum [(2 Rows 8 teeth), (3 Rows 12 teeth) and (6 Rows 24 teeth)] and three levels of sunflower moisture contents (10, 14, 19 %) were studied. Test results indicated that thebest operating conditions were at a speed of 14.7 m/s, clearance of 4 cm and seeds moisture of 10% (d.b).