Abstract:Taking account of the different object spectrum specificity (cloud ,soil ,vegetation,water and so on) and MODIS instrument channel characteristics,this article proposed the multi-spectral synthesis method for cloud detection for MODIS images.The method is applicable to the different scenes.And moreover ,Precipitable Water Vapor(PWV) is added to detect the thin and transparent cloud.The result shows that the thin and transparent cloud is detected by the content of water.