The ZY-3 satellite is the first civilian optical transmission and three-dimensional mapping satellite with highresolution in China. However, the cloud cover is still one of its main noises. This paper selects homomorphism filtering and improved homomorphism filtering algorithms to remove thin cloud after analyzing a variety of method characteristics of removing the cloud, and compares the two methods from by both qualitative analysis and quantitative evaluation. The result shows that the removal of thin clouds of ZY-3 image based on improved homomorphism filtering method has smaller image distortion, and at the same time, keeps the spatial texture detail, which is more suitable for ZY-3 to remove cloud.