The rigid components are always used in traditional walnut shellbroken kerneltaken device. During working process, the walnut kernel is easy to be excessively broken. The shellbroken rate and kernelunbroken rate are also low and the adaptability for different kinds of walnut is poor. In order to improve the walnut shellbroken and kernelunbroken effect, combining with the current research situation of walnut shell breaking by mechanical approaches, a walnut shearingextrusion flexible shell crushing, kernel taking and shellkernel separating device was designed. Stiffness at different positions of walnut shell was analyzed by theory of elastic mechanics, which contributed critical force of unstability of different positions. Critical force of cracking and breakage at different positions of walnut shell was disclosed. Conditions for crack extension after walnut shell breakage were analyzed and calculated by fracture mechanics theory. The results demonstrated that when the mean crack length is 20mm, the critical external force for crack extension is 191N. The singlefactor experiment was carried out to analyze the impact of the top and low section belt spacing (A), top and low section velocity difference (B) and extrusion included angle (C) on walnut crushing force. In this way, the optimal combination of three factors (A, B, C) can be identified through the orthogonal experiment. The experimental results indicated that with A of 23mm, B of 0.19m/s and C of 45°, the most satisfactory shellbroken effects were obtained, which generated the first grade kernel rate of 75%, the second grade kernel rate of 18%, the kernel cracking rate of 5% and the kernelunseen rate of 2%. In other words, under this condition, the shellbroken rate reached 98% and the kernelunbroken rate reached 93%.