Drought is increasingly becoming a critical global issue, and satellite optical remote sensing provides an essential tool for large-scale drought monitoring and assessment. This study focuses on Lushan City in Jiangxi Province and proposes a method for assessing hydrological drought by monitoring water surface area using multispectral remote sensing. Sentinel-2 MSI data is used to extract water surface areas, and an empirical model calculates Poyang Lake’s water levels at different stages of drought. GF-1 WFV data is then analyzed to explore the relationship between Lushan City’s water surface area and Poyang Lake’s water levels to evaluate regional hydrological drought conditions. The results show that there is a significant correlation between the two, indicating that remote sensing technology is highly accurate and feasible for monitoring hydrological drought. The proposed method offers a new approach for dynamic drought monitoring and evaluation, providing data support for disaster prevention, mitigation, and water resource management.