Abstract: Wheat and rapeseed are the major grain and oil crop in China and their sowing dates are closer. Seed feeding device is the core component of air-assisted centralized metering device which is capable of handling a wide range of seeds with different sizes and shapes. In order to improve the versatility and use efficiency of air-assisted centralized metering device and adjust the feeding rate accurately, the seed feeding device for rapeseed and wheat with staggered arrangement shape hole and combined conical-hole unit was designed. The problems of pulsing phenomenon due to outer grooved wheel metering device of the centralized pneumatic planter and high damage rate of mechanical metering device for rapeseed needed to be solved, and the structure of staggered arrangement shape hole could keep seeding consciously and uniformly. The seed feeding operation included seed filling, carrying and feeding process. The main structural parameters of shape hole and conical-hole unit were determined in this research. These included length, width, depth and cone angle of shape hole which were 8.0 mm, 5.0 mm, 4.0 mm and 14°, respectively. The diameter and number of shape holes in each conical-hole unit were 80 mm and 60, respectively. Mechanical models were established to estimate the seed filling and feeding process. It demonstrated that seed filling and throwing performance were better under the inclined angle of 13.75°-21.20°. Bench experiments were carried out in the seed metering laboratory of Huazhong Agricultural University in 2015 by using Huayouza 62 and Zhengmai 9023 as materials. The experimental factors were inclined angle (0°-30°) with 4 levels and rotational speed (10-60 r/min) with 6 levels in single-factor test. Two-factor full factorial test was designed with number of conical-hole unit (1-6) and rotational speed. The objective values were seed feeding rate, coefficient variation of seed feeding rate and damage rate. The results showed that: 1) The conical shape hole with inclined angle resulted in a better seed feeding performance. When the rotational speed of seed feeding device was 10-30 r/min, the seed feeding performance of conical shape hole with 20° inclined angle was better than that of others. The coefficients of variation of seed feeding rate for rapeseed and wheat were not more than 1.0% and 1.1%, respectively, and their damage rates were both less than 0.1%. 2) With the increase of rotational speed in the range of 10-60 r/min, the seed feeding rate increased gradually, while the coefficient of variation of seed feeding rate decreased first and then rose up. The lowest coefficients of variation of seed feeding rate for rapeseed and wheat were recorded at 20 and 30 r/min, respectively. Thus, the optimum rotational speeds which resulted in the coefficient of variation less than 1.0% for rapeseed and wheat were 10-40 and 20-50 r/min, respectively. 3) The ranges of seed feeding rate for rapeseed and wheat were 28-450 and 95-770 g/min, respectively when number of conical-hole unit and rotational speed changed. The wide range of seed feeding rate could be adjusted to meet the requirements of different sowing width and high operating speed. The quadratic regression prediction models were established to describe different seed feeding rate for rapeseed and wheat. The models were verified with different forward velocity of Dongfanghong-LX854 tractor. The relative errors between experimental and simulated results in seed feeding rate were smaller than 5%. It indicates that the models can predict seed feeding rate and calculate the number of conical-hole unit and rotational speed accurately. The staggered arrangement shape hole and combined conical-hole unit can realize the adjustment of seed feeding rate in wide range for rapeseed and wheat and the damage rate is reduced significantly. The results provide technical support for the adjustment of different sowing width of air-assisted centralized metering device for rapeseed and wheat.