The substitution effect in a series of POM-type reversible gel-liquid phase transformation ionic liquid compounds, [MIMPS]₈P₂W₁₆V₂O₆₂, [MIMPS]₆H₂P₂W₁₆V₂O₆₂ and [MIMPS]₄H₄P₂W₁₆V₂O₆₂, has been investigated. Interestingly, there is an obvious substitution effect on the physicochemical properties of these compounds. When protons are substituted in place of ammonium, both the conductivity and the thermo-stability of the compounds can be increased a lot, and more protons can enhance this tendency.