In agricultural fields with full straw retention, due to the large amount of rice straw and the high humidity and toughness of the rice straw, it is difficult for the wheat to be spread uniformly after wheat planting. To achieve uniform crushed straw throwing in dense fields of rice stubble and high-quality straw mulching in dense fields, the uniform throwing device of a no-tillage planter to perform uniform throwing of crushed straw stubble on fields was analyzed and the device operation mechanism was determined. From kinematics and dynamics analyses of particles of crushed rice straw during spread uniformly, a flexible-body model of crushed straw was developd based on EDEM. By adopting the Box-Behnken design, the cover straw inhomogeneity and percent of pass for scatters width as the evaluation index was set and a response surface test was performed on the rotation speed of throwing impeller, the number of pole tooth blade of throwing impeller, angle of throwing impeller. Through a field verification test, the respective parameters for maximum implementation performances were obtained: when the number of pole tooth blade of throwing impeller was 4, the angle of throwing impeller was 15°, and the rotation speed of throwing impeller was 1195r/min, the cover straw inhomogeneity and percent of pass for scatters width by the models were 80.84% and 9.32%. The research result can provide a theoretical basis and data support for innovating seeding technologies and optimizing equipment to uniform crushed straw throwing in dense fields of rice stubble. The uniform throwing device provided high spreading performance for actual operation. Design and optimization of uniform throwing device by no-tillage planter of wheat after rice provided a theoretical basis and data support for innovating seeding technologies and optimizing equipment to evenly throw.