Abstract: To address the issue of uneven seeding caused by operational speed fluctuations in direct rapeseed seeding machines due to variations in soil moisture content and unstable tillage depth, a speed adaptive seeding control system for precision rapeseed direct seeding machines was developed based on Beidou-radar fusion speed measurement. The research encompasses hardware system design, sensor communication control, seeding rate fitting, control program implementation, and the development of a data interaction visualization interface. The system used a programmable logic controller (PLC) as the core processor and integrated components such as an electric-driven multi-chamber centralized metering device, Beidou speed measurement module, speed measurement radar, and human-machine interface. An adaptive gain velocity measurement algorithm based on confidence evaluation was employed to fuse dual-source velocity information from both Beidou and radar, providing real-time output of the machine's forward speed. By dynamically adjusting the rotational speed of the seed metering wheel in response to velocity fluctuations, the system achieves real-time matching between the seeding rate and operating speed, thereby ensuring the stability and uniformity of seed distribution. The study specifically analyzed the impact of the forgetting factor on speed measurement performance, comparing the speed measurement errors of the combined system under different values (0.2, 0.3, 0.4). The results indicated that when the parameter was set to 0.4, the algorithm achieved a balance between noise resistance and dynamic response characteristics. Under various working conditions, the mean absolute error (MAE) of the fused speed measurement was below 0.099 m/s, and the root mean square error (RMSE) was under 0.113 m/s, enabling real-time and accurate output of the operating speed. Based on this fused speed measurement algorithm, the system dynamically adjusted the seed metering wheel speed according to the operating speed, achieving precise matching between the seeding rate and operating speed. This effectively solved the problem of poor seeding quality caused by speed fluctuations. To verify the control accuracy and stability of the rapeseed speed-adaptive seeding system, this study conducted performance tests on a centralized metering device using the rapeseed variety ‘Hua you za 62’ as the experimental subject. Bench test results demonstrated that the average seeding quantity error of the speed-adaptive system was 3.57%, which was lower than the minimum error of constant-speed seeding (4.55%). The coefficient of variation for total seeding quantity stability was less than 2.05%, indicating that the system maintained high seeding uniformity across different working conditions. Field trial results indicated that under various operating conditions (target seeding rates of 3750 g/hm²、4500 g/hm²、5250 g/hm²; operating speeds of 6 km/h and 8 km/h), the average relative error of the real-time rotational speed of the metering wheel was 3.17%. The monitored rotational speed and the theoretical speed exhibited high consistency along the time axis, demonstrating that the speed-adaptive seeding system responds rapidly to velocity changes with minimal dynamic lag, fulfilling the real-time requirements of speed-adaptive control systems. Furthermore, the rotational speed tracking curves showed no significant fluctuations across different operating conditions, indicating the robust performance of the system under multi-variable coupled conditions and its adaptability to complex field operations. Additionally, the average seeding rate error was 4.49%, and the average coefficient of variation for seeding uniformity was 9.41%, both of which comply with the technical requirements for mechanized rapeseed sowing. The research findings suggest that this system can enhance the quality of rapeseed sowing and provide technical support for precision operation.