Abstract: The stable soybean line Xu9302 was used as the test material, and a pot experiment was conducted to study the effects of foliar application of α-naphthaleneacetic acid(NAA) on plant growth and sucrose transport and metabolism in soybean under drought stress at the flowering stage. The results showed that drought stress significantly inhibited the overall growth of soybean. However, the roots were less inhibited than the shoots, leading to an increased root-shoot ratio. Meanwhile, the lateral roots were less inhibited than the primary roots, resulting in a decreased dry weight ratio of primary root to lateral root. Drought stress caused sucrose accumulation in leaves and a decrease in sucrose content in primary and lateral roots, indicating a sourcesink carbon allocation imbalance. NAA treatment significantly reduced sucrose content in leaves while increasing sucrose content in lateral roots, promoting the transport of photosynthetic assimilates from leaves to lateral roots. At the molecular level, drought stress significantly suppressed GmSUT2 expression in leaves and roots but up-regulated the expression of GmMST2, GmCWIN1, GmVIN1 and GmVIN3 in primary roots and GmMST2, GmCWIN1, GmVIN1 and GmSuSy1 in lateral roots. Under drought conditions, exogenous NAA further enhanced GmSUT2 expression in leaves and synergistically up-regulated the expression of the aforementioned sucrose transport and decomposition related genes in both primary and lateral roots, with a greater upregulatory effect in lateral roots than in primary roots. In conclusion, under drought stress at the flowering stage, exogenous NAA improved soybean drought resistance by modulating sucrose transport and degradation, thereby redirecting carbon sources to lateral roots and accelerating their utilization to stimulate lateral root growth.