The invention relates to a testing technique of mechanical properties of materials, in order to provide a material testing device under a high-pressure-hydrogen environment based on ionic liquids and an operation method. A high-pressure hydrogen environment box of the device is internally provided with a cylindrical sample support; the lower end of a loading rod is connected with a power output device of a host machine, and the upper end of the loading rod penetrates through an end cover, and extends into the sample support to be connected with a sample fixture; the ionic liquids are filled in an internal space below an open pore in the top of the sample support; a balance cavity is arranged at the bottom of the end cover, and is composed of an extending section of the tail end of the end cover, a piston connected with the loading rod and a seal bottom cover of the balance cavity; and the loading rod is provided with a load sensor. According to the invention, the balancing cavity and the high-pressure hydrogen environment box transfer pressure by utilizing the ionic liquids, and the hydrogen leakage hazard generated when the pressure is transferred by using hydrogen is prevented; and high-pressure dynamic seal elements, rather than high-pressure hydrogen, in the device, are all in contact with the ionic liquids, thus hydrogen leakage is prevented, and the device safety is improved.