The performance of soil-breaking and root-cutting cutters with different structural forms is quite different. To better break the soil compaction structure of the grassland, the structural design and parameter optimization of soil-breaking and root-cutting cutters were carried out. The discrete element method was applied to construct the grassland soil model, and the parameters of the model were calibrated by direct shear test. A three-factor, five-level quadratic orthogonal rotational combination design test was conducted with cutting edge angle, sliding angle, and cutting tooth angle as test factors, and tillage resistance, soil disturbance area, and specific resistance as target parameters, and a grassland verification test was conducted for the optimal parameter combination. The experimental results showed that when the cutting edge angle was 37.8°, the sliding angle was 33.6°, and the cutting tooth angle was 51.8°, and the operation effect was the best. Grassland tests showed that compared with the triangular soil-breaking and root-cutting cutter, the reduction rate of the optimized soil-breaking and root-cutting cutter was 11.8% and 12.8%, respectively in grassland soil of different firmness, and no significant overturning was produced after the operation, which was more in line with the agronomic requirements of grassland operation. The research results could provide a theoretical basis for the standardized design of soil-breaking and root-cutting cutter.