Abstract: This paper aims to analyze the change of dry-wet condition of Shaanxi Province, China during 1959 to 2014, to provide reference for understanding the regional response and mechanism of the global changes and the improvement of agricultural ecologic environment. The daily data of 20 meteorological stations from 1959 to 2014 in Shaanxi Province were collected to analyze the spatial and temporal change of dry-wet condition by using the methods of humidity index, Morlet complex wavelet and Mann-Kendall test and so on. The results show as follows:(1) The surface humidity index in Shaanxi Province was slightly decreasing in fluctuation and the rate of change was -0.05·(10 a)^-1, but this tendency was not significant, which showed the slightly trend to drought. It was relative arid in spring and winter, but the summer and autumn surface were humid relatively in recent 56 years. There were significant development trend toward acidification in spring and humidification in winter in the past 56 years, however, the development trend toward humidification and acidification in summer and autumn were not significant.(2) Periodic oscillation with multiple time scales of annual and seasonal humidity index in Shaanxi Province were exist which the oscillation cycle were 25-32, 12-15 and 5-10 years throughout the year.(3) There was an abrupt drying point in 1990 at the inter-annual scale. At inter-seasonal scales, the jump points of autumn and winter respectively were in 1976 and 2001, while there were no mutation phenomena in spring and summer.(4)The annual mean surface humidity index of the south and southwest part of Shaanxi Province was higher than that of the north and northeast part. There was an obvious spatial difference of the tendency rate of surface humidity index which were negative in most areas, and the amplitude of drying was greater than that of wetting. At the inter-annual scale, the drying regions mainly included northern Shaanxi, Guanzhong and western part of southern Shaanxi; the wetting areas were mainly distributed in the eastern part of southern Shaanxi. At the inter-seasonal scale, an obvious regional differentiation of the tendency rate of surface humidity index was observed in different seasons, which showed that there were drying tendency in all areas and Guanzhong was the most significant drying area, the area turning to be wet was larger than that turning to be dry in summer and the amplitude of wetting was greater than that of drying, all parts of the study area except Yulin turned to be dry in autumn and the most obvious drying areas were mainly in Guanzhong and the southeast part of southern Shaanxi, the area turning to be wet was also larger than that turning to be dry in winter and the most obvious wetting areas were mainly in Guanzhong and the north part of southern Shaanxi.

Key words: humidity index, Morlet complex wavelet, Mann-Kendall test, spatial and temporal change, Shaanxi Province