Abstract: Abstract: Seed filling performance plays an important role in seed feeding quantity and uniformity in air-assisted centralized metering system. Wheat seed's filling performance in seed feeding device is not good due to its poor mobility and large repose angle. In order to improve wheat seeds' filling performance, seed churning device as a part of seed feeding device was designed. The major components of seed churning device which was installed in seed filling room included churning tooth and shaft. It transported seeds to seed filling zone and increased seeds' compressive force. The main factors affecting seed filling performance included the seed churning tooth's shape, length and its arrangement, the diameter of churning shaft, and the ratio of rotational speed between seed churning device and feeding mechanism. Seed churning tooth's shape included cylinder and cuboid and its arrangement consisted of double helix, line arrangement and cross arrangement. Mechanical models were established to estimate the seed filling process under the effect of seed churning device. It demonstrated that seed filling performance was correlated with lateral force of seeds related to seed churning device's force. In EDEM(engineering discrete element method)simulation, the effects of installation location of churning device on seeds' compressive force, tangential force, number of seeds in shaping hole and its coefficient variation were studied. The seed filling performance of churning device was investigated in bench test. Two shapes and three arrangements of seed churning tooth were evaluated for filling angle, which was measured by high speed camera using pco.dimax HD system, number of seeds in each shaping hole and seed filling failure rate at 3 lengths of churning tooth (4, 6, and 8 mm). The effects of number of conical-hole wheels, rotational speed ratio between seed churning device and feeding mechanism, and rotational speed were evaluated by examining the mean seed feeding rate, coefficient of variation of seed feeding rate and seed damage rate using three-factor full factorial test. Results showed that: 1) Seed feeding device with churning device gave superior filling performance at all treatments by increasing seeds' compressive force, tangential force, number of seeds in shaping hole, filling angle and seed filling rate. Higher compressive force, tangential force and number of seeds in each shaping hole were observed at larger lateral distance and lower longitudinal distance. The seed feeding device with a location of churning device (-65, 5) produced superior results with 1.92 seeds in each shaping hole and a coefficient of variation of 4.05. 2) Seed churning tooth's length affected filling angle and number of seeds in each shaping hole significantly and number of seeds in each shaping hole was different significantly among different arrangements of churning tooth. The ranking order of the factors affecting filling angle and number of seeds in each shaping hole was: churning tooth's length > arrangements of churning tooth > churning tooth's shape. The seed feeding device with a churning tooth's shape of cylinder, a churning tooth's length of 6 mm, and an arrangements of churning tooth of double helix produced superior results with a filling angle of 78.20°, and a number of seeds in each shaping hole of 1.73 and its coefficient of variation of 0.69%. 3) Seed feeding rate increased with the increasing of number of conical-hole wheels, rotational speed ratio between seed churning device and feeding mechanism, and rotational speed. Optimization of the regression equations incorporating number of conical-hole wheels and rotation ratio through multi-objective programming revealed that the rotational speed ratio between seed churning device and feeding mechanism was 1.154 and the number of conical-hole wheels was 6. Based on the optimized operational parameters, seed feeding rate and its coefficient of variation were 690-1340 g/min and 0.23%-0.80% with rotational speed of 20-40 r/min, respectively. Results suggest that seed churning device can improve seed filling and feeding performance. Through the investigation of seed churning device involved in this research, it may contribute to optimizing the structure of seed feeding device and improving the filling performance.