The control of gob water hazard is the key work of prevention and control of mine water in recent years, and the main content of the “11th Five-Year Plan” period of coal mine safety production and research work. Based on the data of water quality of Jincheng coal mine, the evolution of quality of gob water and formation mechanism of acid gob water are discussed, the causes of acid gob water and the water quality characteristics under various conditions of the mining space are analyzed, which provides a reference to distinguish the source of mine water inrush and predict the acid gob water and prevention water work.