An oblique taper holetype wheel centralized metering device for rapeseed and wheat without cleaning and protection device was developed to satisfy the requirements of planting rapeseed and wheat in the middle and lower reaches of the Yangtze River in China,and to improve the efficiency of the planter and simplify the structure of the planter.The key component of the metering device was the holetype wheel designed with two rows of staggered holes for rapeseed and three rows for wheat.An oblique tapered hole structure was developed to prevent seed from plugging holes and reduce the damage rate of seed.The mechanical model of filling,carrying,throwing,and delivering seed were established.The results showed that the minimum height of the seed filling was 10 mm lower than the reference height.The rationality of the device structure was verified.The maximum seeding angle of rapeseed and wheat reached 40.8° and 34.4° when the back angle of the hole ranged from 0° to 30° and from 0° to 15°,respectively.The angle between the seed tube and the horizontal plane should be no less than 33°.The results of orthogonal test showed that the back angle of the hole was 20°,the filling height was the reference height,the rotation speed was 20 r/min for rapeseed.The back angle of the hole was 5°,the filling height was 20 mm,the rotation speed was 15 r/min for wheat.The variation coefficient of the consistency of each line displacement was less than 6.00% for rapeseed and 6.32% for wheat.The coefficient of variation of total displacement stability was less than 1.25% for rapeseed and 1.00% for wheat.The damage rate of both rapeseed and wheat was less than 0.5%.The results of field test showed that both rapeseed and wheat had good sowing.It will provide a reference for designing the structure of mechanical seed metering device for rapeseed and wheat.