The walnut kernel matures more rapidly than hull matures in the areas where climate is dry and hot. Early harvest of mature nut has the advantage of providing higher quality kernels. At this stage of havesting, the hull removal is very difficult. Thus, there is a need to develop mechanisms and machine for removing the hull from the muture nuts. In order to improve the quality of hulling and reduce the damage rate during hulling walnuts, in this article, three factors affecting hulling rate and damage rate were analyzed through orthogonal test on self-made walnut hulling test rig. The results show that, the first greatest effect on damage rate is the diameter of steel wire, the second is the clearance between steel wire tip and hulling cylinder, and the last is hulling cylinder speed. When the hulling cylinder speed is 25 r/min, the diameter of steel wire is 2.3 mm, the clearance between steel wire tip and hulling cylinder is 50 mm, the quality of walnut hulling is the best.