A network switching system is used for monitoring an operation status of an in-line device, including an operating voltage of a hardware unit of the in-line device, an operating system running in the in-line device and at least one application running in the operating system. Once an abnormal status is detected in any of the operating voltage of the hardware unit, the operating system and the application, the network switching system switches a working mode of the in-line device from a normal mode to a bypass mode, to ensure normal communication between first and second network devices connected to the in-line device.