Abstract: For the drawback of artificial unattended drainage system of coal mine, we optimized the drainage system and achieved automatic drainage.By adopting the liquid level switch to detect the water level changes and according to the principle of electrical QBZ-80 starter, the system not only realizes the automatic start-stop of pump through changing the water level,but also can automatically alarm and continue to drain in specific cases, which provides effective protection for pumps and other mechanical and electrical equipment.