The shearing properties of soybean straw were studied by using microcomputer controlled electron universal testing machine. The effect of the straw moisture content, the shear angle and the cutting edge angle on the shear strength and specific energy were scored by using the comprehensive evaluation of the membership-degree method. The quadratic polynomial regression model was established to optimize the shearing parameters by response surface methodology. The results showed that shear angle had most significant effect on the shearing properties, while the cutting edge angle had the least effect. The optimal conditions to shear the soybean straw were the straw moisture content of 25%, the shear angle of 60°, and the cutting edge angle of 45°, under which the comprehensive score was 0.969.