The invention discloses a coalbed gas reservoir reforming method of bottom plate developing mylonite coal, and belongs to the technical field of coalbed gas mining. The reforming method comprises the following steps that a, according to the coalbed total thickness and the mylonite coalbed thickness in a coalbed gas reservoir of the bottom plate developing mylonite coal, the position of a hole-making operation layer section and the position of a hydraulic sand fracturing operation layer section are determined; b, hole-making operation is conducted on the hole-making operation layer section, and a pressure relief space of the preset size is formed in the hole-making operation layer section; c, the bottom of a coalbed gas well and the pressure relief space are washed, and coal dust of the bottom of the coalbed gas well and the pressure relief space is discharged; and d, hydraulic sand fracturing operation is conducted on the hydraulic sand fracturing operation layer section, so that a coalbed collapses to form a crack channel. By means of the reforming method, the production rate of coalbed gas of the coalbed gas reservoir of the bottom plate developing mylonite coal can be improved remarkably.