Proposed is a warning system which includes: a warning device; a display device; an IC CPU for controlling the operation of the display device and the warning device; and a master ECU for, connected to the IC CPU through a communication channel and connected to one or more warning devices through a hardware channel, controlling the operation of the warning device through the IC CPU. The master ECU includes an error detection module to monitor regularly the data validity of the communication channel, the warning device and the response of the IC CPU, and an on/off module to operate the warning device. When the error detection module detects an error in the data validity of the communication channel, the warning device and the response of the IC CPU, the master ECU controls the on/off module to operate directly the warning device using the hardware channel.