Intensive soil loosening and moldboard plowing expose the soil to severe erosion. Conservative tillage is defined as any tillage and planting system that maintains at least 30 percent surface residue cover after planting. In this research, the field performance of a conservation sub-surface tillage tool named double bent-blade sub-surface tillage tool was evaluated. Forward and backward double bent-blade sub-surface tillage tools with two bend angles (10 and 20 degrees) and two rake angles (7.5 and 15 degrees) were designed and constructed. The sub-surface tillage tools were evaluated and compared with a winged chisel tine (control) in a clay loam soil at two water contents (0.7 PL and 0.9 PL; plastic limit) using a randomized complete block design at Isfahan University of Technology Research Farm. Draft, specific draft, cross-sectional area of disturbed soil, soil up-heaving area, clod mean weight diameter (MWD), surface residue cover, after tillage were measured or calculated. Soil water had a significant effect on draft, specific draft, MWD and surface residue cover of the control treatment while no significant effect on measured parameters of the double bent-blade sub-surface tillage tools was observed. Draft was increased as the bend and rake angles increased. The lowest draft value was obtained with the backward double bent-blade sub-surface tillage tool having a 10-degree bend angle and a 7.5-degree rake angle. The draft of the control was significantly higher than the sub-surface tillage tools. In double bent-blade sub-surface tillage tools, the soil failure was initiated from the side edges of the blades and therefore was perpendicular to the direction of the travel. This resulted in wider soil disturbance area as compared with the control. The highest area of the disturbed soil was obtained with the forward sub-surface tillage tool having a 10-degree bend angle and a 15-degree rake angle. The specific draft was affected by the bend angle and it increased with an increase in bend angle. The least specific draft, which means more soil loosening efficiency, was occurred in both types of sub-surface tillage tools with a 10-degree bend angle and a 15-degree rake angle. The specific draft of the control tool was significantly higher than the sub-surface tillage tools. The tool type and its rake angle had significantly effects on MWD. The MWD in forward sub-surface tillage tools was significantly less than the backward ones. Increasing the rake angle resulted in lower MWD. The lowest MWD was occurred in forward sub-surface tillage tool with a rake angle of 7.5 degree and a bend angle of 10 degree. The MWD of all sub-surface tillage tools was significantly lower than the control. The surface residue cover with the control tool was significantly lower than the sub-surface tillage tools. The rake angle of sub-surface tillage tools had a significant effect on soil up-heaving. The soil up-heaving increased with increasing rake angle. The forward sub-surface tillage tool with a 10-degree bend angle and a 7.5-degree rake angle having significantly lower draft and MWD and higher surface residue cover could be suggested as the best alternative for the winged chisel tool in conservation tillage system.