The invention relates to an energy efficiency control terminal and method focused on optimized operation of a central air-conditioning host system. The energy efficiency control terminal is based on an embedded development and is characterized in that an embedded hardware platform mainly consists of a central processing unit, a sampling control module, a communication module, a storage module and a man-machine interaction module; an embedded software system comprises a device driving layer, a system operating layer, a communication protocol layer and an application layer. An optimal control method of the central air-conditioning host system comprises the steps of respectively configuring a host energy-efficiency control terminal, a chilled water pump energy-efficiency control terminal and a cooling water pump energy-efficiency control terminal, and mutually cascading and cooperatively operating the three terminals, wherein a power constant value controller and a temperature difference constant value control for optimizing the energy efficiency of an air-conditioning system are arranged in each terminal, and a voltage constant value controller for guaranteeing the stable operation of a motor is also arranged in each terminal.