Abstract: In order to avoid the distortion of breeding test data caused by remnant and mix of seeds in the internal shell cover in harvest process, adopting field breeding harvest test with self-developed 4GX-100 type cropland plot wheat seeds combine harvester, using the quadratic regression orthogonal rotational combining design, the relationships of no seeds remain rate with threshing cylinder rotation speed, feed rate and suction fan rotation speed were studied, and the mathematical model between operating parameters and the no seeds remain rate was established. The result showed that the effect degrees of 3 factors on the no seeds remain rate was as following: threshing cylinder rotation speed > feed rate > suction fan rotation speed. Through the simulating excellent-choosing equation, the best parameter combination under the field breeding harvest experiment conditions was obtained as following: the threshing cylinder rotation speed was 1586r/min, the feed rate was 0.305kg/s, the suction fan rotation speed was 1076r/min, and the no seeds remain rate was achieved maximum of 99.98%, at this time, which could meet the needs of plot seeding harvester.