A high dynamic range image synthesis method based on camera array is proposed as for the characteristics of space target images in the sky background. The camera array system is used to obtain different exposure images in the same spatial area and the star centroid is used as the control point. Thus the registration of images among different cameras is realized. Combined with the inverse response function of each camera, the weight function is reasonably constructed, and the different exposure images after registration are thus combined into a high dynamic range image. The experimental results indicate that the dynamic range of the synthesized image is increased. The proposed method can be used to effectively improve the signal-to-noise ratio of images, which overcomes the problem of over-damping and over-saturation of target images and is conducive to the detection and extraction of targets.