Abstract: Indocalamus latifolius is a bamboo resource with significant economic value in China, but its leaf yield is prone to decline due to summer drought. This study investigated the response mechanisms of I. latifolius to different drought stress by analyzing biomass allocation, root morphology, root architecture, and non-structural carbohydrate (NSC) allocation, aiming to provide a scientific basis for water management of this species. The results showed that the biomass of leaves, stems, rhizomes and roots decreased significantly under drought conditions, root length, root surface area, root diameter, root tip number, root volume, fractal dimension, root branching angle, and the ratio of root length in the >2 mm diameter grade all decreased significantly, whereas specific root length and the ratio of root length in the (0, 0.5 mm diameter grade increased significantly. Soluble sugar and starch contents in leaves and stems decreased significantly, while the soluble sugar contents in roots and rhizomes increased significantly. The ratio of soluble sugar to starch in leaves, stems, rhizomes, and roots increased significantly. In conclusion, drought significantly inhibited the growth of aboveground parts, rhizomes and roots of I. latifolius, ultimately leading to a reduction in leaf yield. To adapt to drought conditions, I. latifolius enhances the growth priority of roots under “carbon starvation” by increasing the root-shoot ratio and NSC contents in roots, as well as by enhancing specific root length, and the ratio of fine roots, reducing root branching intensity and branch angle and various things like this to the plasticity in root morphology and architecture.