The invention discloses a fire disaster early-warning system for an unmanned communication machine room. The system comprises an AC anomaly detection circuit connected with a power-frequency power supply network, a breaker module connected with the power-frequency power supply network, a standby power supply module used for supplying power to the internal circuit of a cabinet, a power-switching circuit module connected with a power-frequency power supply module and the standby power supply module, a master control module, a linear thermal detector module used for monitoring the temperature of a cable under a conductive floor inside the machine room, an infrared beam smoke-sensing fire detector module used for monitoring the burning smoke of array computers arranged in parallel inside the machine room, and an air conditioner exceptional power utilization alarm module used for monitoring the power utilization condition of an air conditioner. According to the technical scheme of the invention, a fire disaster in the machine room and caused by different reasons can be timely found out at the initial stage. Meanwhile, protection measures are automatically taken and the alarm is conducted.