The invention relates to a crystal form of a renal outer medullary potassium channel inhibitor and a preparation method thereof. In particular, the present invention relates to a III crystal form of L-tartrate of a renal outer medullary potassium channel inhibitor (ROMK) inhibitor and a preparation method thereof. The III crystal form has good chemical stability and crystal form stability, and the crystallization solvent used has low toxicity and low residue, and can be better used for clinical treatment.本發明關於一種腎外髓質分泌鉀通道抑制劑的晶型及其製備方法。具體而言，本發明關於一種腎外髓質分泌鉀通道(ROMK)抑制劑的L-酒石酸鹽的III晶型及其製備方法。該III晶型具備良好的化學穩定性和晶型穩定性，並且所用結晶溶劑低毒低殘留，可更好地用於臨床治療。
