In the context of global climate change, the precipitation variability has intensified, leading to more frequent drought occurrences. Drought has severely impacted agriculture, ecology and the social economy in our country, and agricultural drought is a major factor restricting agricultural development and food security. To achieve refined drought diagnosis during the maize growing season and improve the accuracy of drought assessment. Daily meteorological and agricultural meteorological data of typical stations were selected across different climatic zones in China (Baoding of semi-humid region, Pingliang of semi-humid and semi-arid region, Qingyang of semi-humid and semi-arid region, Dingxi of semi-arid region and Wuwei of arid region) from 1961 to 2023, The continuous days without available precipitation (Dnp) was used as a drought index to refine the effective precipitation threshold and the drought classification standard within the agricultural drought index. Using the improved Dnp drought index, we calculated the drought index for maize growing season across different climate zones, and obtained the drought frequency and interdecadal variation characteristics for the maize growing period. The interdecadal variation of drought was analyzed. The results showed that the Dnp varied during the maize growing period. Except Qingyang and Wuwei, the Dnp showed an increasing trend. During the vegetative growth stage, the Dnp for maize showed an increasing trend, except for Pingliang and Wuwei. During the reproductive growth stage, the Dnp for maize showed an increasing trend, except Wuwei. From the 21st century onward, the Dnp exhibited a rapid increasing trend during the whole maize growth period, with a parabolic trajectory characterized by an initial rise followed by a decline. Except Pingliang and Wuwei, the Dnp showed an increasing trend during the vegetative growth stage of maize. The interdecadal variation of the Dnp showed an increasing trend during the vegetative growth stage of maize, except Wuwei. The frequency of interdecadal drought in maize varied across different climatic zones. Baoding experienced the highest drought frequency, while Wuwei and Dingxi had the most frequent and most severe drought events. Except for Baoding, the overall drought frequency showed an increasing trend. Additionally, the frequency of severe drought increased in Pingliang and Qingyang. The findings offer technical support for drought monitoring, drought assessment, and disaster prevention and mitigation efforts.