Based on climatic information and hydrologic data of the headstream and mainstream areas of Tarim River, basic hydrological processes of Tarim River basin, changes of precipitation and temperature of mountainous areas, water condition of the headstream areas and water resources consumption in each river reach of the mainstream are analyzed. Characteristics of hydrological process of Tarim River Basin in recent 50 years are analyzed primarily and discussed. The results show that specifically natural condition of Tarim River basin results in forming runoff area, water resources utilization area and water resources consumption area are separate each other. For global climate changes, the temperature and precipitation of mountainous areas are both increasing. Runoff of the headstream areas is increased greatly. The Akesu River, which is the most influencing on the mainstream areas, turns into especially high water period. However, stream flow of the mainstream areas has a decreasing slightly trend. With the increase of water consumption in the upper reaches of Tarim River, ecological environment in middle and lower reaches of Tarim River is degenerated obviously.