In order to detect distribution range and expansion features of coal bed washout in 4013（ 26 ） working face of Tieshannan Mine of Sichuan Dazhu Coal Electricity Group, feasibility of detecting coal bed washout by radio wave penetration instrument was discussed and fixed-point perspective method was used on the basis of communication theory of radio wave in mine. The results showed that the technique had a good effect on distribution law of coal wash zone and severity of washing in working face. Combining with analysis of regional geological data, abnormal area caused by erosion in coal mine could be divided and structural features in working face could be predicted accurately, which was an ideal and reliable technological means to detect coal bed washout in working face.