Great financial losses and safety loophole will be caused by water gushing accident in coal mine. The vast original water inflow data come from one FuXin coal mine is used to establish dynamic the gray G(1,1) model for water inflow forecast with gray system theory and method. Its characteristics are simple structure, less calculated amount and good adaptability. The Siemens S7-300 series PLC and configuration software are used to finish high efficiency and energy saving integrated automation control in underground drainage system. It is safe and reliable and can be used to increase production efficiency, save energy and reduce cost. Log monitor and auto run are realized. The results show that the model can precisely predict water inflow with good reliability and instantaneity.