The invention discloses a rock mechanics three-axis testing high-pressure kettle, is designed for solving the problems of high machining cost, relatively large size and the like of equipment. A kettle body of the high-pressure kettle is arranged in a three-axis rack; a kettle cover with a central piston hole is connected and arranged at the top end of the kettle body, and a bearing base sealed by an annular sealing ring is connected to the bottom end of the kettle body; an axial loading piston sealed by an annular sealing ring is arranged in the kettle body, and a balance communication tube for communicating an upper space and a lower space of the piston is arranged on the sidewall of the kettle body; a piston rod on the upper part of the axial loading piston penetrates through the central piston hole in the kettle cover and sealed by the annular sealing ring, and the top end of the piston rod is connected with the top surface of the three-axis rack. The high-pressure kettle realizes the pressure self-balance by the balance communication tube arranged on the kettle body, and thus the pressure born by the three-axis rack is reduced, an application of the three-axis rack can be relatively economic, relatively simple and relatively convenient, and relatively safe, the manufacturing cost spent on the high-pressure kettle is greatly saved, and a three-axis compression experiment is facilitated.