For the problem of the picking roller of present half-feeding peanut harvester was easily wrapped in plastic membrane, a kind of peanut removing device used spiral knife was designed. The structure optimization and experiment analysis were also carried out. The helical blade was modeled based on UG software. The best arrangement of the blade was confirmed by stress nephogram. Through the analysis of experimental data and processing, the best structure and operating parameters of the proposed device were got: the clearance was 5.3mm, speed of picking roller was 326r/min, and arranging blade angle was 43°. After optimizing, the breaking membrane rate value reached to 95.66%.