Acidic properties of silica-rich metallosilicates, which are effective for selective hydrocarbon syntheses, were investigated through computer simulations adopting a Monte Carlo method on adsorption of NH3, methanol, H2O, and some hydrocarbons. The results of the simulations were compared with experimental data and their validity were confirmed. The unique catalytic performance of different kinds of metallosilicates could be explained according to the microscopic description of their acid sites.