The laser active imaging can overcome the disadvantages of passive imaging under low light conditions，but the SNR of the images is usually severely disturbed and enhancement algorithm is needed to improve the contrast.Because the laser images gotten at different time have great difference，the characteristics of images under night and twilight conditions are discussed.Through analyzing and summarizing its characteristics and classification method，adaptive enhancement algorithm of laser image based on histogram fitting and brightness decision is proposed.Quadratic function fitting histogram is adopted to determine image capture time；the best homomorphic enhancement threshold is found through the luminosity function，and the images at different time are classified.The experimental results show that the histogram fitting quadratic function has high accuracy，and adaptive homomorphic enhancement algorithm can effectively improve SNR and contrast of the images.