Abstract: According to a high ccst, ambiguity, low small fault detection accuracy and other problems existed in conventional detection technology, a method with m any gas drainage boreholes in coal mine was applied to detect the hidden small faults was conducted. Taking a mining strip through seam applied to pre- drainage the s eam gas region as the study object, based on the data from the gas drainage boreholes, the control point coordinates of the seam floor were calculated, the contour ma p and 3D map of the pre- drainage strip seam were drawn and then the quantitative predictions were conducted on the certain location, attitude and throw of the hidden small faults in coal seam. The site experiment was applied to investigate the spacing control of boreholes, fault throw and borehole depth error affected to the detection accuracy of the hidden faults. The results showed that the higher fault throw was, the smaller spacing between boreholes and the smaller error of the borehole depth W as, the higher detection accuracy would be. With the method, a fault throw of 2.5 m was successfully detected.