In order to achieve precision seeding of low sowing quantity of wheat and improve the accuracy of precision seeding of wheat, a kind of cone diversion type horizontal plate wheat precision seed-metering device was proposed. The design and theoretical analysis of key parameters were carried out. Single factor test on the effects of the guide bar form, number of holes, cone disc speed and cone disc angle on seed-filling performance were studied by EDEM discrete element software, and then the parameters were determined. On this basis, the multiple quadratic regression rotation orthogonal combination test was carried out with cone speed, seed-layer thickness and length of hole, and then the test data was analyzed by Design-Expert 8.0.6 software. The regression model and the influence of factors on the index were obtained. The influence relation of factors on the single rate was determined and the order of importance was the cone disc speed, length of hole and seed-layer thickness in turn. The order of importance of the qualified rate was the cone disc speed, seed-layer thickness and length of hole in turn. Interaction between the length of a hole and the seed-layer thickness, cone disc speed and seed-layer thickness cannot be ignored. Based on the regression model, the parameters were optimized and the seed metering device under the optimized parameter combination was tested for seed-metering performance. The results showed that the qualified seed-metering rate, the leakage rate and single rate was 90.13%, 9.87% and 49.50%, raspectively, and the test results matched the simulation optimization results. The reliability of the simulation optimization result was verified. The performance comparison tests with the original cone seed-metering device showed that the designed cone diversion type horizontal plate wheat precision seed-metering device was better than the original cone disc seed-metering device in both metering performance and breakage index. The qualified rate was increased by 3.4 percentage points, 2.1 percentage points and 1.9 percentage points at 3km/h, 4km/h and 5km/h, respectively, and the damage rate was decreased by 0.2 percentage point at 3km/h. The designed cone diversion type horizontal plate wheat precision seed-metering device can effectively improve seed filling performance and qualification index and reduce sowing quantity and breakage rate. The research results provided a reference for the design of wheat precision seeder used in wide seedling strip.