Aiming at the characteristics of poor resolution,low contrast,low signal-to-noise ratio,blurred visual effect,complex human posture,multi-obstacle occlusion,incomplete human posture and so on of fire infrared images.In this paper,a human body detection algorithm based on U-Net network for fire infrared image is proposed.The algorithm solves the difficulties of complex human body posture,multi-obstacle occlusion and incomplete human body shape in fire scene.At the same time,compared with the traditional target detection algorithm and the YOLO v3 algorithm,the proposed algorithm has greatly improved the detection accuracy and real-time operation of fire infrared image human body detection.