In order to explore the structure and function of the high affinity potassium transporter gene of Phytolacca acinosa Roxb(PaHAK1) and analyze the reasons of tolerance to low potassium in Phytolacca acinosa Roxb, the amino acid sequences and protein structures and physicochemical properties of 15 high affinity potassium ion transporters in HAK/KUP/KT gene family of Arabidopsis thaliana and PaHAK1 of Phytolacca acinosa Roxb were compared . The results showed that all coding proteins were orientated on cell membrane, and they contained multiple transmembrane domain with conserve amino acid sequences. The transmembrane structure of PaHAK1 was very similar to that of AtKUP3, and the high expression of PaHAK1 and AtKUP3 under low potassium stress was closely related to the high affinity potassium transport and absorption function. Phylogenetic analysis showed that PaHAK1 had the closest evolutionary relationship with AtKUP8 in Arabidopsis thaliana HAK gene families. Their amino acid sequences similarity was 76.98%. It is suggested that PaHAK1 also plays an important regulatory role under water stress by maintaining a high level of intracellular potassium.