Aiming at the problems of low detection accuracy, large data fluctuation and weak robustness of the detection system of traditional single UAV equipped with nuclear radiation detector, this paper constructs a nuclear radiation detection system based on multi-UAV cooperation. Firstly, a multi-UAV formation control algorithm is designed to realize the cooperative control of multi-UAV. Secondly, a multi-sensor extended Kalman data fusion mechanism is improved to fuse the radiation data collected by multiple sensors into a more accurate radiation data, which improves the detection accuracy of the system. Finally, the system is successfully deployed to the physical platform, and the feasibility of the system is verified. The experimental results show that the system can reduce the detection error by about 50% compared with the single sensor system, and improve the robustness of the system. The improved extended Kalman data fusion algorithm can reduce the fusion error by about 21% compared with the ordinary extended Kalman data fusion algorithm.