Since 1990, Tamsagbulag`s and Zuunbayan`s deposits of East Mongolia have been intensively explored. Our experts consider the deposits in Tamsagbulag as the most prospective areas. This study aims at determining physicai and chemical characteristics of petroleum, drilled in wells of Tamsagbulag and Zuunbayan areas. The study on chemical, physical characteristics, heteroatomic compounds, compositions of main oil fractions, group composition of hydrocarbons in gasoline fractions of East Mongolian petroleum was successfully carried out for the first time. The petroleum of Zuunbayan`s deposit rich in paraffins and heavy oil fractions is preferred for paraffin-bitumen orientation for the petroleum processing. On the contrary, petroleum of Tamsagbulag`s deposit rich in gasoline and kerosene fractions is preferred for gasoline-kerosene-diesel production orientation for petroleum processing. On the basis of these results a feasibility study for an oil processing plant in Mongolia is discussed.