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ABSTRACT The harvesting of straw by the flail knife type straw cutting device will cause loose contacts between straw roots and soil, affecting the straw feed's impurity content. In this study, a theoretical analysis of the straw cutting process was conducted to explore the factors influencing the root-soil disturbance. A pulling force test device was designed to test the pulling force of the corn stalk. The response surface method was used to study the effects of various factors on the straw pulling force under different conditions of draft angles (20°, 30°, 40°), soil moisture content (15.23%, 17.62%, 20.47%), and different straw root diameters. The test results showed that the straw pulling force was directly proportional to the straw root diameter and inversely proportional to the soil moisture content. The straw pulling force decreased first and then increased with the increase of the draft angle. According to the established second-order regression model, when the draft angle was 28.5°, the soil moisture content was 20.47%, the root diameter was 22 mm, the minimum pulling force of straw was 189.635N. The test results can provide a reference for the design of straw feed harvester.