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As a corn harvester for reaping both corn stalk and spike needs high efficiency and performance to harvest corn cob and corn stalk, a stalk chopper (SC) in horizontal roller type was designed. Aiming at studying the effect of parameters of chopper on picking and smashing performance, the working principle of SC was analyzed. Box-Benhnken Design（BBD）response surface method was used to design the field experience. An orthogonal rotary combination experiment was conducted with the working speed of corn harvester, the fixed angle of cutting knives and rotating speed of SC as three independent factors, as well as broken rate and loss rate of corn kernels, average length and geometric standard deviation of smashed corn stalk as four dependent indices, while using corn named Zhengdan as the test materials. Corn cobs, kernels and stalks were collected manually and calculated to get the results after every experiment. Design-Expert software was employed to analyze the test data, and mathematical equations between independent and dependent factors were gained. The results indicated that the independent factors had a second nonlinear relationship with dependent indices, while only working speed of corn harvester and rotating speed of SC had significant effects on loss rate of corn kernels. Three factors all had significant effects on other dependent indices. The interaction between working speed of corn harvester and rotating speed of SC had a significant effect on broken rate of corn kernels and average length of corn stalk. Parameters optimization showed that when working speed of corn harvester was 1.35m/s, the fixed angle of cutting knives was 52°, rotating speed of SC was 1350r/min, the device had optimal performance with loss rate of corn ear of 1.1%, broken rate of corn kernels of 0.23%, loss rate of corn kernels of 0.74%, average length of broken stem of 30.73mm, and geometric deviation of 1.28. Compared with field test results, it was showed that the regression equation had a good prediction. In contract to the test with working speed of 1.11m/s, fixed angle of 53°, rotating speed of 1657r/min, the results showed that under optimal conditions loss rate of corn ear, broken rate of corn kernels, loss rate of corn kernels, average length of broken stem and geometric deviation were reduced by 0.4%, 0.784%, 1.318%, 12.20mm and 0.34, respectively. The research result provided a basis for the stalk chopper of corn harvester for reaping both corn stalk and spike.