Abstract: The Northwest China is very sensitive to the climate change. The trend of climate change in Northwest China is divided into four climate states, as Ⅰ state(from 1961 to 1990),Ⅱ state(from 1970 to 2000), Ⅲ state (from 1981 to 2010) and Ⅳ state(from 1961 to 2013). Using the annual average temperature, annual average precipitation, daily max temperature extreme, and daily precipitation extreme data in Northwest China, we analyzed the effect of climate state change on extreme weather monitoring. The results showed that the influence of climate change on average annual temperature was more obvious than annual precipitation. There is the phenomenon of temperature rise under the Ⅰ state and Ⅱ state, and there is the phenomenon of temperature decrease under Ⅲ state during the temperature evaluation analysis. Climate states change have little impact on precipitation levels. The extreme daily max temperature event and extreme daily precipitation event increased under three climate states in 1970s and from 1990s to 2010s, and the amplification is biggest under Ⅰ state, and is most little under Ⅲ state. In Northwest China, the main sensitive areas to the climate states change are northwest Xinjiang, north Qinghai, the center and east of Gansu, most of Ningxia and some area of Shaanxi.

Key words: climate state, extreme monitoring, sensitive area, Northwest China