The characteristics of geographical distribution and season change of clouds over Northwest of China are analyzed based on the International Satellite Cloud Climatology Project(ISCCP) mean monthly data from July 1983 to December 1993. It is shown that the cloud amount distribution over Northwest of China is coherent with orographic distribution. There is the least cloud amount over the Tarim Basin, where the dominant clouds are relatively thinner in cloud layer, such as cumulus and high level clouds. There are the extremum regions of the cloud amount over the Tianshan Mountains, the Kunlun Mountains, and the Qilian Mountains, where the dominant clouds are relatively thicker in cloud layer, and relatively greater in vapor amount, such as stratus, nimbostratus, and deep convective cloud.What is worth noting is that the spatial and temporal distributions of cloud have distinguished stability and local features, which benefits to the artificial rain enhancement.