Breaking of walnut shell with less damage remains to be a challenge because walnut kernel is crisp. The existing equipments which were used to break shell and take kernel cannot meet the high quality and mass requirements of walnut kernel. Aiming to resolve the above gaps, the cam rocker bidirectional extrusion self-positioning walnut shell breaking device were designed. By analyzing the critical condition of crack fracture, the mechanism of crack propagation and the displacement of breaking walnut shell, the double-screw quantitative feeding mechanism and cam rocker bidirectional extrusion breaking mechanism were designed. The size of the extrusion/blanking U-shaped block structure, the motion angle and displacement of the cam mechanism were determined, the rocker displacement equation was determined and the cam profile curve was designed. L9(34) orthogonal test was carried out with extrusion clearance, camshaft rotation speed and walnut circumference size as test factors, and one kernel rate, two kernel rate, nibs rate and hulling rate as test indexes. The results showed that the primary and secondary order of the various affecting factors were the walnut circumference size, extrusion clearance and camshaft rotation speed, and the optimized combination was as follows: the walnut circumference size was 34~37mm, extrusion clearance was 7mm, camshaft rotation speed was 53r/min. Taking the optimal combination for verification experiment, the results showed that one kernel rate was 61.39%, two kernel rate was 23.30%, nibs rate was 15.31% and hulling rate was 92.36%. Compared with the traditional walnut sheller and kernel extractor, the high kernel rate was increased by 14.69 percentage points, which met the walnut industry primary processing needs.