The invention discloses an anti-theft alarm system of a power cable. The anti-theft alarm system comprises an anti-theft alarm subsystem, alarm signal processing equipment and multiple alarm signal terminals. The alarm signal terminals are mounted on outgoing line cables connected with a transformer substation respectively and comprise a signal generating device and a first transmitting device, the signal generating device is used for generating corresponding alarm signals when predetermined conditions of the power cable installed on the signal generating device occur, and the first transmitting device is used for transmitting the alarm signals to the alarm signal processing equipment; the alarm signal processing equipment is arranged inside the transformer substation and comprises a signal receiving device used for receiving the alarm signals transmitted by the first transmitting device, a signal processing device used for processing the received alarm signals and a second transmitting device used for forwarding processed results to the anti-theft alarm subsystem; the anti-theft alarm subsystem comprises alarm apparatus used for alarm. According to the anti-theft alarm system, the power cable can be prevented from being stolen.