Aiming at the problems existing in the open-loop electric-driven seeding process of rapeseed and wheat for the current centralized air-conveyed combined seeder for rapeseed and wheat, such as the lack of dynamic response of seeding rate to the operating speed of the machine and real-time monitoring of the machine's operating status, which result in large errors in the actual seeding rate of the seeder and cumbersome operation procedures for the operator, a speed-adaptive control system for rapeseed and wheat air-assisted centralized metering device was designed. The system was controlled by an STM32 microcontroller. Utilizing human-machine interface information exchange to adjust the seeding rate, precise speed measurement via non-contact radar, and real-time operation posture detection through an inclination sensor, it realized the selection of seeding conditions and accurate identification of the operation state for the seeder, combining with the speed adjustment of the metering device and the dynamic matching of the metering device's drive logic, the automatic control of the electric drive seeding for rapeseed and wheat was achieved. The experimental results showed that the radar field speed measurement method had an error of no more than 2.76% and a stability variation coefficient of no more than 4.12% under different ground conditions, significantly outperforming the ground wheel encoder speed measurement method. The inclination sensor had an angle detection error of 0.13°~0.15°, enabling accurate detection of the seeder's operating posture. Under the field seeding conditions, the control system could achieve speed-adaptive seeding for both rapeseed and wheat at different operating speeds, with the control errors of rapeseed and wheat sowing rates being less than 2% and 3.5%, respectively. The field experiment results showed that when the seeder equipped with the speed-adaptive control system was actually used in field operation, the consistency variation coefficients of the number of plants per row for rapeseed and wheat were 8.59% and 12.96%, respectively, meeting the requirements of the sowing operation standard for rapeseed and wheat. Moreover, compared with the traditional open-loop uniform speed drive method of the seed metering motor, the consistency variation coefficients of the number of plants per row for rapeseed and wheat were decreased by 8.33 percentage points and 5.06 percentage points, respectively.