Through the montmorillonite settlement experiment in the clear water and electrolyte solution, the influence of slime water settling character was studied in clear water and different electrolyte solution, the montmorillonite＇s hydration ex- pansion effectively restrained was verified, the process method to wash coal with the electrolyte was put forward, and the re- sults indicate that the solution of 10 g/L KC1 is optimal inhibitor on the montmorillonite in the tested three kinds of electrolyte solution. With the contrast test in clear water and electrolyte solution, two reagent adding way can be selected in KC1 solution： one way is to add PAM separately, the effectively sedimentation can be made with simply 0.1% anion; the other way is the co- ordination with polymeric aluminum and PAM, the anionic of PAM and polymeric aluminum are 0.02% and 0.5% respectively. However, in clear water, the polymeric aluminum must be joined together with the anionic PAM, and the amount of the PAM reaches 0.5%, which is 25 times as great as that in KCL solution. The field work with raw coal further verifies the above con- clusions further.
