Abstract: Millet is a characteristic crop of semi-arid regions, with high drought tolerance and stable yield. The semi-arid region of Inner Mongolia and Hebei is the dominant millet production region, with the highest planting area and total yield of millet in China. Drought is threatening millet production in this region. In order to reveal the impact of drought on the millet growth processes and increase the capacity of millet production to cope with drought, the crop water deficit index (CWDI) was used to investigate millet drought in this study. Based on the daily meteorological data from 27 meteorological stations in the study area from 1961 to 2019, the temporal and spatial variation characteristics of the millet drought were analyzed by combining drought intensity, drought frequency, and drought station ratio. The results showed that:（1）in the past 60 years, the drought intensity of millet in the semi-arid area of Inner Mongolia and Hebei showed a significant downward trend. The frequency and station ratio of millet drought decreased with increased drought level.（2）The drought intensity and frequency in each growth stage of millet was in order of: jointing period>seedling period>maturity period>grain filling period>heading period. （3）The drought intensity and frequency of millet decreased gradually from northwest to southeast while the occurrence range of moderate drought, severe drought, and extreme drought decreased with time. The reduced intensity and frequency of drought is in favor of millet production in semi-arid region of Inner Mongolia and Hebei.

Key words: Semi-arid region, Crop water deficit index, Millet, Growth stage, Drought intensity and frequency