Background Plant genomes contain large number of HAK/KUP/KT transporters, and they play important roles in potassium uptake and translocation, osmotic potential regulation, salt tolerance as well as root morphogenesis and plant development. Potassium deficiency in soil of main sugarcane planting area is serious. However, the HAK/KUP/KT gene family remains to be characterized in sugarcane (Saccharum). Results In this study, 30 HAK/KUP/KT genes were identified from Saccharum spontaneum. Phylogenetics, duplication events, gene structure and expression pattern were analyzed. Phylogenetic analysis of HAK/KUP/KT genes from 15 representative plants showed that this gene family were divided into four groups (clade I-IV). Both ancient whole-genome duplication (WGD) and recent gene duplication contributed to the expansion of HAK/KUP/KT gene family. Nonsynonymous to synonymous substitution ratio (Ka/Ks) analysis showed that purifying selection was the main force to drive the evolution of HAK/KUP/KT genes. The divergence time of HAK/KUP/KT gene family was estimated to range from 134.8 to 233.7 Mya based on Ks analysis, suggesting that it is an ancient gene family in plants. Gene structure analysis showed that HAK/KUP/KT genes was accompanied by intron gain/loss in the process of evolution. RNA-seq data analysis demonstrated that HAK/KUP/KT genes from clade II and III mainly displayed constitutive expression in various tissues, while most genes from clade I and IV had no or very low expression in the tested tissues at different developmental stages. SsHAK1 and SsHAK21 displayed upregulated expression in response to low K+ stress. Conclusions This study provided insight into the gene evolutionary history of HAK/KUP/KT genes. HAK7/9/18 were mainly expressed in the high photosynthetic zone and mature zone of stem. Moreover HAK7/9/18/25 were regulated by sunlight. SsHAK1 and SsHAK21 played important role in mediating potassium acquisition under limited K+ supply. Our results provide valuable information and key candidate genes for further study on the function of HAK/KUP/KT genes in Saccharum.