Abstract: In order to resolve the problem of redundant harmonic noise exist in data of underground channel wave and affect the accuracy of the channel wave dete ction, we analyzed the cause of harmonic noise on geophones, and propose a method to adaptive attenuate harmonic noise on underground geophones. The method a daptive filter out the abnormal frequency on common receiver gather, and eliminate harmonic components of singles come from each detector without damaging the cha nnel wave. The method has been applied in a detection of sinkholes in a coal mining face. The result showed it could effectively reduce harmonic components of data fr om geophones, improve the quality of transmitted channel wave and the accuracy of CT result, decrease the noise caused energy attenuation coefficient of the experim ental data from 0. 058 to 0. 035, and reduce the influence of the noise of harmonic wave on geophones to the image of sinkholes.