Abstract: In this paper, statistical methods, such as the quartic polynomial, maximum entropy spectral analysis and MannKendall test, are used to analyze the daily precipitation data observed by 78 selected meteorological stations distributed evenly in Shaanxi Province during the period from 1961 to 2004, and the heavy precipitation days are acquired by defining heavy precipitation. The results show that the variability of heavy precipitation days was high, and drought and flood occurred easily in Shaanxi Province. The heavy precipitation days was increased after the end1990s. Under the reliability level of α=0.1， a sharp decrease of heavy precipitation days occurred during the period from the end1980s to the early1990s. Heavy precipitation days were increased from the north to the south, and there were two centers with more heavy precipitation days: one was near Yijun, and the other was near Zhenba. The daily maximum precipitation in the Guangzhong region was in an increase trend in recent 40 years, and it was increased by 1.5 mm every ten years. The intensity of heavy precipitation was also increased.

Key words: heavy precipitation, precipitation days, climate change, Shaanxi Province