DYC-JQ electro-vacuum differential Pressure valve is a safely valve for mechanical vacuum pump. It is mounted at the intake nozzle of mechanical vacuum pump, synchronously opened and closed with the pump. In case that pump stops working or power supply is suddenly broken off, valve disc will be closed automatically under atmospheric pressure, to keep the vacuum system vacuum and the air charged into pump cavity, thus to prevent pump oil from reverse flow that can pollute the vacuum system. Applicable medium can be pure air or noncorrosive gases.