Sishui County is surrounded by mountains in the north and south, with a terrain that is high in the east and low in the west, belonging to the Yimeng Mountain range. To accelerate the treatment of rural domestic sewage, actions were carried out in Sishui County to improve rural domestic sewage treatment and explored a new treatment approach. The widely promoted composite biological purification tank method is a reference for promoting rural domestic sewage treatment in other mountainous and hilly areas.