The Heihe River is a bigger inland drainage running through the three provinces of Qinghai, Gansu and Inner Mongolia in the northwestern China as well as the biggest river in the Hexi inland region. The Qilian Mountains lying in the northeastern brim of the Qinghai Tibet Plateau is the formation region of the surface water resources in the Heihe river basin. Because of the existence of the hydrometric factors closely related with the temperature such as mountain glacier, snow cover and frozen earth etc., the runoff is also sensitive to the temperature besides the atmosphere precipitation supply. According to the fourth scientific evaluation report on climate change issued by IPCC in February, 2007, it is predicted that the global average temperature will be raised by 1.8～4.0℃. During the last century (1906-2005), the global average surface temperature has risen by 0.74（0.56～0.92）℃，which is higher than 0.6（0.40～0.80）℃ which is the rising temperature extent in recent 100a（1901-2000 a）issued in the third evaluation report by IPCC in 2001. In the warmest twelve years since 1850, there are eleven months appearing in the year of 1995-2006 except 1996, and the rising temperature rate in the past 50a is almost twice of that in the past 100a.The forecasting result which has synthesized the results of various GCMs under various SRES shows that by the end of this century, the temperature of the global surface will have increased by 1.1～6.4℃ and the rising extent of the global sea level will be 0.18～6.4°m^[1]. In the future 20a, the air temperature will increase at the speed of about 0.2℃/10a, even if all the greenhouse gas and aerosol are stabilized at the level of 2000, and the climate will still get warmer, and some of the changes will be more obvious than those of last century. According to the first evaluation report on the global climate changes and the countries influenced issued by National Climate center, China Meteorological Administration in January 2006, the rising temperature rate in China in the past 50a is quite obvious, among which the climate change in the Qinghai-Tibet Plateau locating on the high altitude zone is especially focused upon.It is forecasted that the temperature will be getting warmer and warmer in future and the annual mean temperature will increase 1.3～2.1℃ by 2020 and 1.5～2.8℃ will increase and 2.3～3.3℃,and the annual precipitation will increase 2%～3% by 2020 and about 5%～7% by 2050 in China. The change on water cycle and the redistribution of water resources on space and time must be caused beca use of the difference of heated condition and the change of atmosphere circumfluent. The drought in the middle latitude zone in the Northern Hemisphere and the lack of water resources in some regions will be caused by the persistent global temperature rise, and at the same time, the regional environment and the development of society and economy will be affected. So study of the changes of the water cycle factors such as air temperature, precipitation, runoff in the mountainous areas of the Heihe′ main river under the global warming is of all greatly important meaning for the continual utilization and development of water resources in the Heihe river basin and the whole Hexi Inland River Basin. Therefore, based on observational data ground temperature, precipitation and runoff of the resent 50a at the weather stations in the mountainous area of the Heihe′ main river basin, the variation characteristics and trends of the annual mean precipitation in the region are analyzed. The results show the response of the mean temperature in the region to global warming is quite obvious. Even the rising extent of temperature in the area is higher than that of the global warming. At the same time, the precipitation and runoff also present an increase trend and the increase extent of runoff is bigger than the precipitation, which means the increase of runoff is not absolutely rely on precipitation. According to the variation trend of temperature and precipitation in the area,it is forecasted that the runoff in the mountainous area of the Heihe'main river will presents a little increasing trend in the future 50a.The runoff in the area will unceasingly increase, the same as that in the past 50a, unless the extreme climate combination appears, and the increase extent will be less than 10% of the present mean value.