A high-temperature biaxial strength tester for a CMC turbine vane includes a test stand, a thermal insulation box, a vane fixture, a biaxial loading device, thermocouples, a multi-channel thermometer, quartz lamps, a digital image correlation (DIC) system, and a cooling circulation system. The biaxial loading device includes two loading mechanisms arranged at 90° to each other. Each of the two loading mechanisms includes an electric cylinder and a ceramic push rod. One end of the ceramic push rod is connected to the electric cylinder, and the other end of the ceramic push rod extends into the thermal insulation box to contact an outer platform of the CMC turbine vane. The electric cylinder is provided with a load-displacement sensor. The thermocouples are arranged on the thermal insulation box. The quartz lamps are arranged inside the thermal insulation box. The multi-channel thermometer is connected to the thermocouples.