BACKGROUND Colocasia esculenta L. Schott is a main traditional root crop in China, serving as an important vegetable and staple food. Drought stress plays vital role on the growth and development of taro corm. METHODS Two different varieties of taro in Jiangsu were selected: Xiangsha taro and Longxiang taro. The accumulation characteristics, morphological structure, and physicochemical properties of taro corm starch were studied by microscopic observation, particle size analysis, and X-ray diffractometer (XRD) analysis. Transcriptome analyses were used to identify the related genes of taro corm under drought stress. RESULTS During the growth of taro, the number of amyloplasts showed an obvious increasing trend and shifted from being dispersed throughout the cells to being gathered on one side of the cells, and morphological observations showed that smaller granular distribution gradually changed to a larger lumpy distribution. The particle size of Longxiang taro is smaller than that of Xiangsha taro. Under drought stress conditions, the occurrence of starch grains and corm size were inhibited in Xiangsha taro. Transcriptome sequencing of drought-stressed taro corms showed that the enzymes related to starch synthesis were differentially expressed. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of drought-stressed taro corms showed that drought affected hormone signal transduction, material metabolism, drought stress tolerance, plant growth and development, and stress resistance, which triggered the plant drought adaptive response. CONCLUSIONS Drought stress inhibits starch accumulation in taro.