The invention discloses an early-warning device of a converting station spare channel. The early-warning device of the converting station spare channel comprises a microprocessor, a channel monitoring plate socket, a universal serial bus (USB) interface, a subscriber identity module (SIM) card socket, an indicator light module and a global system for mobile (GSM) chip which are respectively connected with the microprocessor, a power supply and an antenna, wherein the power supply is respectively connected with the microprocessor and the GSM chip, a plurality of channel monitoring plates are inserted into the channel monitoring plate socket; an SIM card is inserted into the SIM card socket; two simulating channels or two digital channels are detected by the microprocessor, and the operation state of the simulating channels or the digital channels is acquired and displayed through the indicator light module; the microprocessor controls the GSM chip to compile warning short messages when the two simulating channels or the two digital channels are out of order, and then the warning short messages are sent to a plurality of mobile terminals through the antenna. The early-warning device of the converting station spare channel detects the condition of a telecontrol channel in real time, reports the operation state to mobile phones of operating personnel by the warning short messages when the channel is out of order, can access to imperative telecommand quantity, and is used as the converting station spare channel.