MTBE (methyl tertiary-butyl ether) is an Oxygenated organic matter which is widely used nowadays in some countries in unleaded gasoline. MTBE is a toxic substance which is absorbed quickly on water and soil and is one of the most important pollutants in soils and groundwater resources. In order to remove MTBE from the soil, using different experimental methods, determining reliable methods for specifying adsorption capacity of MTBE according to optimum value of affecting parameters and MTBE concentration in soil is the first and the most important step. Therefore, in this study contaminated Kaolinite clay soil samples were prepared with different concentrations of MTBE. Afterwards the maximum adsorption capacity of MTBE in the soil and effect of various parameters, such as: sample PH, contact time, MTBE concentrations and soil dosage of samples, on its value was investigated. The results showed that contact time and MTBE concentration have the most effect on maximum adsorption capacity of MTBE in the soil. Maximum adsorption capacity of MTBE in the soil determined equal to 1.15 g/kg considering optimum condition of effective parameters. Since Kaolin clay soils can be widely used certainly for removal of MTBE from contaminated soils, especially through electrokinetic techniques, thus, it is believed that Results of this study experiments provide specific guidance for future researches into MTBE adsorption capacity of Kaolinite.