The study of present-day hydrothermal ore-forming process in Uzon caldera (Kamchatka, Russia) is reported. The structure of ore body and the distribution components are described. Parameters of ore-forming process (temperature, pH, Eh and activity of dissolved hydrogen sulfide) are measured with original experimental devices. Parameters of gas and liquid phase flow and heat of hydrothermal fluid are studied in details. Base on this investigation results, the thermodynamic model of ore-forming process in Uzon caldera is designed. This model includes several ore-forming mechanisms: boiling, cooling and mixing and oxidization of hydrothermal solution. The analysis of thermodynamic simulation results of is compared with the data on mineralogical data and concentration of forms of sulfur that has allowed establishing a role of various ore-forming factors in ore deposition. The new model of hydrothermal ore process which explains formation of the full ore structure as consequence of self-development of thermal solutions is offered. Calculated concentration of the dissolved forms of sulphur and ore components are in the good consent with the natural data. Results of the spent works can be useful at research of hydrothermal deposits and modern geothermal systems.