Based on the daily precipitation data from 740 stations, by means of linear trend estimate, Mann-Kendall test method, the long-term trends and interdecadal variation of precipitation, frequency, contribution to the total rainfall over North China during rainy seasons are analyzed. Some new results are discovered as follows: the rainfall over North China during rainy seasons, and five kinds of precipitation frequency and contribution over North China during rainy seasons have a certain decreased trend with different decreased rates. The most obvious decreased trend is the rainfall over North China during rainy seasons. The long-term decreased trend of the five kinds of precipitation frequency has obvious characteristic of gradual change, and the decreased trend of light rain frequency is biggest while the decreased trend of torrential rain and excessively heavy rainfall frequency is not significant. Meanwhile, the decreased trend of contribution of heavy rain to the total rainfall over North China are biggest. The biggest contribution to the total rainfall over North China is from heavy rain and close to one-third of the total rainfall in the past 50 years. The rainfall over North China during rainy seasons is mainly influenced by the heavy rain frequency and the excessively heavy rainfall contribution. The interdecadal abrupt change took placed in 1978 for both rainfall and excessively heavy rainfall contribution over North China during the rainy season, so the interdecadal abrupt change of excessively heavy rainfall contribution during rainy seasons results in the interdecadal abrupt change of rainfall over North China.