The invention discloses a method for preparing corrosion coal and analyzing and testing physical mechanics weakening characteristic. The method includes (1) preparing corrosion coal: putting corrosion liquid with pH value of 4-10 into a corrosion case, starting a heater, putting the coal test piece and coal sample with size of 4-60 mesh into the corrosion liquid, performing sealing with a sealant, starting a swirl generator, and waiting 1-60 days; (2) analyzing the mesostructure of the coal test piece and the change of the metallographic structure; and (3) performing uniaxial compression test and gas-containing triaxial compression test for the coal test piece, performing uniaxial compression test after pressing the coal sample to be coal test piece, and testing the change of the mechanical characteristic. The method can be used for improving the working solution to improve the effect of hydraulic permeability improvement measure by means of researching the physical mechanics weakening characteristic of the corrosion coal, provides support for the gas control, can effectively simulate the change of the coal body in the deep mine under the effect of underground drainage, and provides support for the research of the rule of the mine geological disaster in the complicated condition and the prophylaxis and treatment of the mine geological disaster.