A kind of walnut cracking machine with self-grading extrusion which combined the walnut grading with cracking shell was designed and developed, which integrated the two working procedures of walnut grading and cracking shell. This machine mainly consisted of variable-frequency motor, frame, adjusting plate, grading device, cracking shell device, gap adjusting device and so on, and the cracking shell gap and the motor speed could be adjusted. The machine had the characteristics of compact structure, easily to be operated and so on. The Wen-185 walnut was selected as the test object, and the cracking shell tests of prototype were carried out. The results showed that the optimum parameters of cracking walnut were that the opening size of adjusting plate was 70 mm, motor speed was 150 r/min, cracking shell gap was 10 mm. In the condition of optimum parameters, the average value of one-time cracking shell rate was 93.2%, and the rate of high grade kernel was 89.8%.