High-Affinity K + transporters/K + Uptake Permeases/K + Transporters (HAK/KUP/KT) are important pathways mediating K + transport across cell membrane, which function in maintaining K + homeostasis during plant growth and stress response. An increasing number of studies have shown that HAK/KUP/KT transporters play crucial roles in root K + uptake and root-to-shoot translocation. However, whether HAK/KUP/KT transporters also function in phloem K + translocation remain unclear. In this study, we revealed that a phloem-localized rice HAK/KUP/KT transporter, OsHAK18, mediated cell K + uptake when expressed in yeast, E. coli and Arabidopsis. It was localized at plasma membrane. Disruption of OsHAK18 rendered rice seedlings insensitive to low-K + (LK) stress. After LK stress, some WT leaves showed severe wilting and chlorosis, whereas the corresponding leaves of oshak18 mutant lines (a Tos17 insertion line and two CRISPR lines) remained green and unwilted. Compared with WT, the oshak18 mutants accumulated more K + in shoots but less K + in roots after LK stress, leading to a higher shoot/root ratio of K + per plant. Disruption of OsHAK18 doesn't affect root K + uptake and K + level in xylem sap, but it significantly decreases phloem K + concentration and inhibits root-to-shoot-to-root K + (Rb + ) translocation in split-root assay. These results reveal that OsHAK18 mediates phloem K + loading and redistribution, whose disruption is favor of shoot K + retention under low-K + stress. Our findings expand the understanding of HAK/KUP/KT transporters' functions, and provide a promising strategy for improving rice tolerance to K + deficiency.