The results of the research revealed a possibility to use the gas composition for analysis of the formation processes of the Mutnovsky geothermal fluid. CO2/H2S value shows significance of endogenous components, whereas O2/N2 value shows the significance of meteoric components. A hydrogen behavior is a possible result of the geodynamic condition. Different boreholes within Mutnovskaya geothermal station have their own peculiarities. These peculiarities are probably connected with their structural position within the geothermal reservoir.