Under 60℃ circumstance, with X'Pert PRO X Ray, Spectrometry Electron Microscope, Scanning Spectrometer and so on, the concentration changing law of main ions is systematically investigated in the residual acids after montmorillonite mineral, whose content is over 98%, reacts with HF, HF/HCl, HCl/HBF4. Solid phase transformation, characteristics of particle fabric, and factors of affecting the transformation etc have also been researched. The experiment results indicate: acids have capability to dissolve Al element of montmorillonite crystal initially. HF/mud acid reacts with montmorillonite at a very fast rate, showing fast and intensive dissolution characteristics. In the reaction less than 2 hours, 8% HBF4 system turns into weak acid and the main ions content is only 1/2 to 1/3 of that in HF or mud acid; after 2 hours, HBF4 system has identical dissolving endurance of montmorillonite; with Spectrometry Electron Microscope, complicated scale has been found, which is likely to damage reservoir bed.