Abstract: Aiming at problems of high threshing loss and crushing rate of buckwheat, a buckwheat threshing device was designed by using combination of telescopic rod tooth and grooved rod combined buckwheat threshing device and elastic adjustable concave plate． Structure and parameters of key components were designed． Matlab/Simulink software was used to establish dynamics analysis of threshing device's key components． Analysis results showed that threshing device ran smoothly when mechanism was working, maximum power consumption of drum resistance was 0.53 kW, and power consumption of torque to maintain uniform rotation of drum was 3.11 kW, and overall power consumption was small． Using Design-Expert software, two-factor and five-level quadratic regression orthogonal rotation combined experiment was carried out with drum speed and threshing gap as experimental factors and threshing loss rate and breakage rate as evaluation indexes, and parameters of test results were optimized． Results showed that, under conditions of buckwheat grain moisture content of 17.5%-23.2% and straw moisture content of 70%-74.9%, when feeding amount was 2 kg per group, drum speed was 457.161 r/min, threshing gap was 12.6815 mm, it was the best experimental combination, and its threshing loss rate was 0.337% and breakage rate was 0.236%． Test results could meet design requirements．