Based on the daily precipitation observations of 740 stations in China from 1960 to 2000，the abrupt change point of power-law exponents of daily precipitationof 0—7mm in north China，northeast China and northwest China is located exactly on 1979. This indicates that the large-scale climate background of these regions has changed at that time，and it has close relation with the index MEI.This maybe one of the main reasons for the drying trend of north China.The 0—29mm daily precipitation is to some extent a stationary process，and the daily precipitation being≥30mm is obviously non-stationary，which makes the long-term prediction of heavy rainfall very difficult.