Weibei Loess Plateau is an important grain production base of Shaanxi Province. In this study, in order to promote the ability for coping with drought, daily precipitation data from 1986 to 2015 of this region were selected, and the standardized precipitation index (SPI) was calculated as an indicator to quantitatively analyze the temporal and spatial characteristics of drought in this area. Results showed that: (1) In the recent 30 years, SPI varied with the precipitation except some particular months. That is because the sensitivity of SPI to precipitation differed in different time scales. (2) Dividing the SPI into different time scales, can better reflect the development status and trend of drought and flooding. The short time scale (1 month) was used to reflect the drought variation monthly, while the medial scale (3 months) can be used to reflect the drought variation by season. In addition, the longtime scale (12 months) was observed to reflect the moisture hysteresis effect. Through the analysis of SPI in multiple time scales, the Weibei Loess Plateau presented a tendency of being wet, and the randomness of SPI declined with the increase of time scales, whereas the duration strengthened. Corresponded to the climate change, the drought frequency declined. (3) It was tested to be drought in 1993, 1994, 1997, 1998 and 2001, in this area. Meanwhile, according to the SPI, the spring and summer are much more prone to be drought than the autumn and winter, which can be concluded to be higher frequency during dry seasons. (4) The drought condition was relatively consistent within the whole Weibei Loess Plateau. The results for Weibei Loess Plateau will provide a scientific basis for agricultural drought management and decision-making.