Regulation of K⁺/Na⁺ homeostasis is an important mechanism in plant growth. The high-affinity K⁺ uptake system plays a central role in this mechanism especially when plants experience environmental stresses of K⁺ starvation and high salinity. K⁺ channels and the K⁺/Na⁺ co-transporter like HKT have been closely studied as principal members of the K⁺ transport system in plants. The KT/HAK/KUP family is a major K⁺ transporter family present in bacteria, fungi and plants. In plants, the KT/HAK/KUP transporters form a large family. Arabidopsis thaliana has 13 genes and rice has at least 25. KT/HAK/KUP transporters serve various functions in various K⁺ traffic, but their physiological roles are still unclear. Plant KT/HAK/KUP transporters could be divided into 4 related clusters according to their amino acid sequences, the character of transporters belongs to each cluster was summarized. We analyzed the expression of OsHAK genes in rice roots under both K⁺ starvation and salt stress conditions.