Abstract: The technics of ammonia synthesis and the character of bed temperature control for quench ammonia synthetic tower are analyzed.Several stair-like generalized predictive controllers are constructed for the bed temperature of sections in the tower.These temperature control loops are associated by feedforwards of previous section temperature.The feedforwards of pressure,raw gas temperature,content of circular hydrogen and ammonia condensation temperature are introduced into the control system,and the supervisory shell for the controller is designed.The application effect verifies good control quality of this control system.