A multi-band monopole antenna includes a first metal radiator and a second metal radiator extending in a same direction and arranged in parallel for exciting a high frequency band, and a detoured wire pattern connected between the feed end of the first metal radiator and the connection end of the second metal radiator for exciting a low frequency band. The detoured wire pattern has a, circuit path length longer than one half of the high frequency band λ/2 so that the phase difference on current between the feed end of the first metal radiator and the connection end of the second metal radiator is about π(180-degrees); the electric fields generated at the lower sides of the first metal radiator and the second metal radiator have approximately the same size but reversed phases and the magnetic fields have the same characteristics; when the reversed phases of electromagnetic waves excited by the first and second metal radiators reach the HAC test surface, they cause a destructive interference, thereby improving hearing aid compatibility performance of the multi-band monopole antenna.