In order to counter the problem of reduced health promotion ability in typical grass with compacted roots, a root-cutting machine was designed for pasture. The machine used cam-driven of direct cutter to cut root vertically, greatly reducing resistance and perturbations of soil surface while cutting the root, which reached easy work in varies of forage. The machine destroyed solid soil, improved grassland, and increased grass yield. As proven by analyzing the velocity, acceleration and force of the machine was able to meet the needs of designing. It is a more ideal agricultural machine for forage grass. 