The theoretical study is designed to determine the cutting angle of the soil processing plant with an active movement, and a vertical axis of rotation. The angle of cutting is formed by the front working surface of the blade and the tangent to the trajectory that passes through the knife blade and coincides with the direction of the cutting speed. The cutting angle during the process of cutting the soil chips is constantly changing depending on the angle of rotation of the knife. As a result of the study the influence of the working mode was established and a theoretical dependence of the cutting angle was derived – αP=αmin+Δαmax-Δα. Its value was determined depending on the mode of operation and design parameters of the working units of the machine.