Aiming to solve the problem of poor seed filling performance and low seeding accuracy of the current pneumatic precision seedmetering device for cottonseed under high speed operation. Based on the structural characteristics of inside-filling seed-metering device, a kind of inside-filling pneumatic high speed precision cotton seed-metering device was developed. During the working process of the seed-metering device, the dual seed filling method combining inside-filling and airflow absorption was utilized in the filling place, and after the action of seed eliminating apparatus, twice seed throwing mode was applied in the throwing place. The mechanical model of seed filling and adsorption were constructed and the structural parameters of key components were determined. In order to explore the performance of seed-metering device, some relevant bench test were carried out with the cotton seed variety E＇kangmian-10 of which the moisture content was 8.92% was selected as experimental material and the qualified index, multiple index and missing index were taken as evaluation indicators. First of all, the single factor experiment was employed with eliminating distance as the impact factor and the optimal one for cotton direction seeding was chosen out. Then based on the above optimal seed cleaning effect, the Box-Behnken rotation-orthogonal combination experiment of three factors and three levels was executed, so as to study the influence law of suction hole diameter, forward speed and vacuum degree on seeding performance and achieve the optimal combination of each factors. Additionally, compared with the traditional vertical disk air-suction seed-metering device, a contrast test of seeding performance under high speed condition was carried out. The results indicated that the inside-filling pneumatic precision seed-metering device had the optimal cleaning effect with the qualified index of 93.14% and missing index of 3.73% when the eliminating distance was set at 2.0 mm. The factors influencing qualified index and missing index of seed-metering device was in the following order as vacuum degree, forward speed and suction hole diameter. The optimal combination was suction hole diameter with 2.9 mm, forward speed with 8.4 km/h and vacuum degree with 1150 Pa under the solution of Design-Expert 10.0.4 optimization module. On the above condition, the qualified index, multiple index and missing index of seeding were 96.48%, 2.41% and 1.11%, respectively. In the range of 8~12 km/h, the qualified index of seeding was more than 91% and missing index was less than 7%, which was better than the seeding performance of traditional vertical disk air-suction seed-metering device and met agronomy requirement for cotton direct seeding.