The invention discloses an automatic leaking detecting and plugging method for a high-level-extraction-tunnel bottom plate. Underholing is carried out at a high-level-extraction-tunnel preset position, and two closed walls are built; the portion between the two closed walls is filled with loess, extraction pipes and a measure pipe penetrate into the upper portions of the two closed walls, one endsof the extraction pipes are located inside a high-level extraction tunnel, the other ends of the extraction pipes are located outside the high-level extraction tunnel and are connected with an external gas extraction pipe, a liquid injection pipe penetrates through the external closed wall, sealing mucilage is injected into the loess through the liquid injection pipe, a water pool is built in thefracture influence range of a bottom plate outside the external closed wall, a water-level automatic detection control device is arranged on one side of the water pool, loess mud water is automatically controlled to be injected into the water pool, and an automatic leaking detecting and plugging function of a high-level-extraction-tunnel bottom plate fracture is achieved. The automatic leaking detecting and plugging method for the high-level-extraction-tunnel bottom plate has the advantages of being good in high-level-extraction-tunnel gas extraction effect, high in extraction efficiency andthe like.