The invention discloses a mining TBM chamber bottom plate hardening method. The method comprises the steps that an originating chamber is made into a circular chamber slightly larger than a cutter head through spray modeling; geosyncline is dug along a first assembly chamber from at least 2.5 m backward from the first assembly chamber to the tunneling working surface of the originating chamber till reaching the hard bottom; multiple groups of column nest tubes are installed in the dug geosyncline, three mutually parallel steel rails are embedded in the middle of each group of the column nest tubes, and corresponding steel rails on the multiple groups of the column nest tubes are connected in sequence; two rails are laid in a second assembly chamber and a third assembly chamber in sequence, the two rails are the first rail and the second rail, concrete pouring is conducted on a rail roadbed and the geosyncline from the second assembly chamber, whole-section floor leveling is conducted on the three assembly chambers, and floors are tangent to the lowest point of the originating chamber after forming. According to the method, the strength of a roadway bottom plate can be effectively improved, the requirements of the overall weight obtained after a shield tunneling machine is supported for assembling for surrounding rock can be met, and the method is simple and applicable.