The structure and motion parameters of corn header have clear influence on working performance of corn harvesting machine. The relationship between picking corn cob power and idling power of ejector roller and the influences of ejector roller speed, auger speed and picking board gap distance on broken rate of corn stalk were studied by field test. The results showed that idling power of ejector roller was larger than its picking corn cob power. The field test also showed that with the increase of ejector roller speed, the lose rate and damage rate of corn ear decreased. When the ejector roller worked in a high speed, the lose rate and damage rate were lower at a larger picking board gap distance. With the increase of ejector roller speed, both broken rate of corn ear and corn stalk decreased. The broken rate of corn ear was lower and broken rate of corn stalk was higher at a larger picking board gap distance.