In complex combat environments, the detection capability of a single UAV is limited, making it unable to effectively complete detection tasks for multiple targets in larger areas. Therefore, the cooperative detection technology of multiple UAVs system is being widely studied. This paper proposes a multi-UAV cooperative detection method based on genetic algorithm. The method divides the detection process into two stages: target assignment and cooperative detection. Taking into account the detection capability constraints of UAVs, optimization objection functions are designed for each stage, and genetic algorithm is used for optimization solution. Simulation shows that this method can adapt to constantly changing detection environments and is effective in improving the target recognition rate and overall detection accuracy of multi-UAV system.