The utility model relates to an electronic device preventing telephone embezzlement, composed of a bridge circuit, an amplifying alarm circuit, an oscillating circuit, an integrated circuit and a recognizing circuit. The electronic device can overcome the defects of polarity connection, short detection, etc., and effectively prevent phone line embezzlement in full lines under the condition of noninterference on the normal operation of a stored-program control exchange and the normal use of a host. The utility model can be made into a telephone terminal box form or arranged in the telephone, and is suitable for the technical field of telephone theft protection.