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Shaker potassium channels play a crucial role in potassium (K+) nutrition and stress resistance in plants. However, systematic research on Shaker K+ channels in Chinese cabbage [<i>Brassica rapa</i> var. chinensis (L.) Kitamura] remains scarce. This study identified 13 Shaker K+ channel members within the cabbage genome, which are unevenly distributed across eight chromosomes. Notably, the number of Shaker K+ channel members in Chinese cabbage exceeds that found in the model plants Arabidopsis (9) and rice (10). This discrepancy is attributed to a higher number of homologous proteins in Groups II and V of Chinese cabbage, with gene segmental duplication in these two subgroups being a significant factor contributing to the expansion of the Shaker K+ channel gene family. Interspecies collinearity analysis revealed that the whole genome and the Shaker K+ channel family of Chinese cabbage show greater similarity to those of Arabidopsis than to those of rice, indicating that Shaker K+ channels from the Brassicaceae family have a closer relationship than that from the Poaceae family. Given that gene expansion occurs in Group II, we investigated whether a functional difference exists between <i>BrKAT1.1</i> and <i>BrKAT1.2</i> using yeast assays and promoter analysis. The expression of two <i>BrKAT1</i> genes in the potassium uptake-deficient yeast mutant R5421 can restore growth under low potassium conditions, indicating their role in potassium absorption. Truncation of the N-terminal 63 amino acids of <i>BrKAT1.2</i> resulted in the loss of potassium absorption capability, suggesting that the N-terminus is essential for maintaining the potassium absorption function of <i>BrKAT1.2</i>. Furthermore, the expression of the two <i>BrKAT1</i> genes in the salt-sensitive yeast G19 enhances yeast tolerance to salt stress. These results demonstrate that <i>BrKAT1.1</i> and <i>BrKAT1.2</i> exhibit similar abilities in potassium uptake and salt tolerance. The difference between <i>BrKAT1.1</i> and <i>BrKAT1.2</i> lay in their promoter regulatory elements, suggesting that differences in transcriptional regulation contributed to the functional differentiation of <i>BrKAT1.1</i> and <i>BrKAT1.2</i>. These findings provide a foundation for understanding the evolution and functional mechanisms of the Shaker K+ channel family in Chinese cabbage and for improving potassium nutrition and salt tolerance in this species through the manipulation of <i>BrKAT1</i>.