The Study evaluated the field performance to sub soiler plow (two tines)from study some factors which effect its field performance such as cultivation depth and the front speed of tractor and verify its effect on the  field  performance  like  power of retract , specific resistant and tractor ability. The study use four plow depths (20,30,40 and 50 cm) and three front speeds (0.27,0.31 and 0.52 m/sec.)in clay soil. The results showed increased the draft force with the increased of plowing depth for all front speeds, the retract draft force increased also with the increased of front speed, while the specific resistant was decreased with the increased of plowing  depth  for all forward speed ,the effect of increased  forward speed lead to increased the specific resistant in ratio 34% , 33% , 43% ,and 36% when the forward speed increased from 0.27 to 0.52 in the depth of 20, 30, 40 and 40 cm   respectively, while  the efficiency of plow increased with the increased of plow depth for all front speeds also the ability increased with the increasing of forward speed in ratio(0.38, 0.36, 0.33 and 0.29 ) when the front speed  increased from 0.27 to 0.52 m/sec. in the depths (20,30,40 and 50) respectively.