The renal outer medullary K+ channel (ROMK) is a member of the inwardly rectifying potassium channel superfamily, which mediates the transport of K+ from renal tubular epithelial cells into the tubular lumen and plays a crucial role in maintaining the body' s K+ homeostasis. Mutations in its gene can cause impaired renal function, characterized by type II Bartter's syndrome with K+ metabolic disturbances. Therefore, alternations in the functional status of ROMK channels can disrupt the transport of K+ and Na+ , as well as the homeostasis of water, electrolyte and blood pressure. Here we review recent progress regarding the ROMK channels in the apical membrane of renal tubules, focusing on their function and the regulation of activity, to provide new insights for the prevention and treatment of clinical conditions involving ion metabolic disorders.