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A stubble cutter was designed with manually variable disc diameter adjustment for the problem that the passive disc stubble cutter on the no-till planter in the no-tillage seeder in the Huang-Huai-Hai wheat and corn area has a low straw cutting rate in the case of large amount of straw cover or insufficient soil strength. The variable-diameter stubble cutting blade was equipped with a disc diameter adjustment mechanism, which can adjust the disc diameter according to the soil characteristics of different fields and the amount of straw stubble cover on the ground surface in order to realize efficient straw cutting. Combined with theoretical analysis, it was determined that the angle of two edges of star teeth of blade was 110°, the minimum radius of variable diameter disc stubble cutter was 230mm, the maximum radius was 280mm, and when the stubble cutter was adjusted to a certain diameter, the variable diameter mechanism had a self-locking function to ensure that the diameter of blade was fixed. The results of soil bin test showed that the diameter of 460mm variable diameter stubble cutting disc, flat disc, notched disc, and corrugated disc, under the same working conditions, the disc into the soil depth was deeper than the shallow cutting performance, into the soil depth of 10cm, variable diameter stubble cutting disc straw cutting performed better than other types of discs, at this time, the straw cutting rate was 75.16%, the traction force was 355.27N. Soil bin performance tests showed that the larger the diameter of the variable diameter stubble cutting disc was, the better the straw cutting performance was. In the disc diameter of 560mm, the straw-cutting rate was 93.25%. Field validation tests showed that the variable-diameter stubble-cutting disc device in the disc diameter of 560mm, the straw cutting rate was 98.33%, which was good to meet the no-tillage sowing operation of the Huang-Huai-Hai regions of wheat agronomic and technical requirements. The research result can provide a reference for the design of the stubble-cutting device for no-tillage implements.