A clear understanding of the drought impact on crops is essential to reduce drought-related yield losses. In this study, a framework to explicitly quantify the impact of drought on a specific crop has been proposed. The sugarcane is selected as the target crop, and the growth process is divided into 4 stages in different areas in Guangxi. The evolution of drought and water requirements, as well as the impact of drought on water requirement and yield are evaluated based on Standardized Precipitation Evapotranspiration Index (SPEI), Crop Water Requirement, and sugarcane Standardized Yield Residual Series. The drought in sugarcane growing season tends to intensify, and the drought risk in Southwest Guangxi will increase. Nevertheless, different drought trends exhibit in different growth stages. During the sugarcane seeding and tillering stages, the drought trend in Guangxi is dominant. Consistent with the detected trend of increasing drought, the water demand of sugarcane in most areas showed a significant upward trend. Crop Water Requirement and irrigation water requirement reached the maximum at the stem extension stage. The relationship between drought and irrigation water requirement varied in different regions. Sugarcane is vulnerable to drought risk during stem extension stage, resulting in a decline in yield, and the water demand at this stage is also the largest. The fluctuation of sugarcane yield can be explained by the interannual variation of SPEI. Specifically, the mid- to short-term drought in August and September have a significant impact on sugarcane production. Short-term SPEI can predict the occurrences of drought events earlier than long-term SPEI, and the fluctuation range is also greater. The severe and long-lasting drought has a serious impact on sugarcane yield. The method is expected to be applied to other crops in other regions.