Abstract:The change of climatological mean value indicates the change of climatic average state (hereinafter referred to as climatic state). Due to the difference between different climatic states, when one climate state changes, it will influence the judgment results of variation characteristics of various meteorological elements, atmospheric circulation system and so on. The greater the difference between different climatic states, the more obvious the impact on judgment results, which is the impact of climatic state replacement. How will the new regulation of changing the climate mean value from 1981-2010 to 1991-2020, which will be implemented on 1 January 2022, affect China’s climate monitoring, prediction and evaluation? This is a very concerned problem in our climate operation. In view of the change of the climatological mean value, this paper compares and analyzes the differences and impacts of climatic states in different periods from the aspects of temperature and precipitation at 160 stations in China as well as from the changes of atmospheric circulation and oceanic key factors and so on, and then focuses on the impacts of the new climatic state replacement of 1991-2020. The results show that the influence of climatic states in different periods is different, in which the influence of temperature climatic state replacement is more significant than that of precipitation climatic state replacement, and there are some seasonal differences in this influence. The influence in winter is greater than that in summer, while the influence of precipitation climatic state replacement is mainly concentrated in the two transition seasons of April-June and September-November. By analyzing the influence of the new climatic state, we found that the temperature anomaly in most parts of China decreases, and the maximum decrease area is near Hetao region, with a decrease range of 0.3-0.7℃. The influence of precipitation climatic state replacement mainly occurs in summer and autumn, and the rainy characteristic in southern China in summer and in northern China in autumn weakens; The influence of height climatic state replacement on 500 hPa atmospheric circulation shows that in winter Ural Mountains ridge is strengthened, the East Asian trough is more eastward and the Mongolian high is weakened, while the situation is just the opposite in summer. In terms of the influence on monsoons, the East Asian winter monsoon is weakened, but the summer monsoon is strengthened. In addition, the IOD positive phase weakens and the sea surface temperature (SST) anomaly index in Ni〖AKn~D〗o1+2 region rises.