Based on the daily precipitation observations of 740 stations in China from 1960 to 2000, this paper expounds the power-law tail distribution characteristic of the daily precipitation ≥30mm in 7 climate characteristic regions, and the power-law exponent γ>3.0 in most part of China. It is found that the daily precipitation ≥30 mm is a non-stationary process, and it makes the long-term prediction of heavy rainfall very difficult. It is also found from further investigation using the filtering method that the power-law tail distribution characteristic is the result of the interaction of atmospheric systems of various scales, among them the one-week scale system has the most important influence on power-law tail exponent of the daily precipitation ≥30 mm.