The present invention provides a computer system, a notebook computer and a method for controlling a computer system. The method comprises steps of: determining current state of the main computer subsystem; turning off the power of the embedded subsystem or enabling the embedded subsystem into a low-power state of the embedded subsystem when the main computer subsystem stays in a power-on state of the main computer subsystem; and enabling the embedded subsystem into an operating state of the embedded subsystem when the main computer subsystem stays in a low-power state or a shut-down state of the main computer subsystem. The computer system comprises: a power supply, a main computer subsystem and an embedded subsystem, wherein the main computer subsystem comprises a state determination module and a state control module for the embedded subsystem. The notebook computer comprises a main board, an embedded subsystem and a power supply, wherein the main board comprises an embedded controller and a power switch controller as well. With the above technical solutions, the power consumption caused by the embedded subsystem is reduced while implementing a preset function in real time.