In order to promote the whole mechanized production of Chinese herbal medicine and solve the problem of no suitable sowing device in the Radix peucedani planting, a kind of wheel seed metering device with guide ring groove combining U-hole was proposed. The structure and working principle of the planter and seed metering device were described. The key structural and working parameters of seed metering device were analyzed according to the shape characteristics and main physical and mechanical parameters of Radix peucedani seed. The mechanical model of seed particle group during seed filling and seed supplying was established. The performance of seed metering device was simulated and optimized by using discrete element software EDEM. The influence of U-hole depth, U-hole width and seed guide ring dip angle on average sowing amount per second and the variation coefficient of seed row uniformity were studied. Box-Behnken response surface optimization method was adopted to carry out three-factor and three-level orthogonal simulation experiment. The average sowing amount per second and variation coefficient of seeding uniformity were 0.199g/s and 12.37%， respectively, when the U-hole depth was 4.65mm, U-hole width was 13.63mm, and the seed guide ring dip angle was 47.01°. A two-factor and five-level quadratic regression orthogonal rotation combined bench test of seed supplying performance was carried out. The test factors were set as the rotation speed of seeding wheel and the initial filling height of seed layer. The test indexes were variation coefficient of uniformity of seeding in row, variation coefficient of total seeding stability, variation coefficient of seeding amount uniformity in each row. Bench test results showed that seed metering device had the best performance when the rotation speed of seeding wheel was 25.69r/min and the initial filling height of seed layer was 46.70mm, and variation coefficient of uniformity of seeding in a row, variation coefficient of total seeding stability and variation coefficient of seeding amount uniformity in each row were 18.62%, 1.60% and 2.96%, respectively. Field test demonstrated that variation coefficient of uniformity of seeding in a row, variation coefficient of seeding uniformity and variation coefficient of seeding amount uniformity in each row were 22.54%, 1.95% and 3.66%, respectively when the planters forward speed was 1.2km/h. The research result can provide reference for the design of seed metering apparatus for flat and irregular shape crops seeds.