Abstract: Xinjiang is the main cotton-producing area in our country, cotton stalk is the crop residues after cotton harvest. In order to avoid the environmental pollution of straw burning caused ,it must smashed the straw quickly after the cotton harvest, or it will directly affect the seed planting in the next year. The current horizontal rotaried smashed straw machine have the problem, which crushed straw length is uneven and stubble is too long. We develop the Y type cutting device of Smashed Straw Machine to solve this problem. Through the oretical analysis of the key working parts of the structure parameters, and orthogonal experiment analysis of the main factors affecting to the quality of machine operation, the optimal working parameters are obtained. By the field test, when the machine speed is 9 km/h, hob rotational speed is 2400 r/min, blade clearance to the ground is 10 cm. Length of straw crushing qualified rate is 87.5%, stubble height is 9.5 cm, fully meet the design requirements. This machine could promote the development of utilization cotton straw and renewable resource.