Abstract: According to No.2 and No.3 mining blocks affected by the mining failure in a small mine, the spontaneous combustion, uncertain conditions of mine wate r ponding and gas accumulation, poor roof support and others in the goaf of Underground No.2 Mine, a transient electromagnetic method was firstly applied to determin e the failure scope of the previous mine, then an advancing borehole was applied to detect the certain geology of the coal mining face and to detect the goaf structure a nd surrounding rock stability of the previous small mine and finally to detect the accurate location of the gateway of the goaf in the small mine, the related location of th e goaf space in the small mine, the inner space size of the goaf in the small mine, as well as the inner water, gas and upbuildings conditions in the goaf of the small min e.A certain backfill re-mining plan was determined finally according to the detection results.With the detection conducted on No.B909 coal mining face, seven goaf in th e small mine within the coal mining face were fully backilled.When the coal mining face moved forward to the backilled goaf, there was no roof leakage and spalling oc curred.