The invention discloses a high temperature three-point bending test system and a high temperature three-point bending test method. The high temperature three-point bending test system comprises an electronic tensile testing machine, a fixture component and a heating furnace for heating a test sample, wherein the electronic tensile testing machine comprises an upper beam and a lower beam; the fixture component comprises an upper fixture and a lower fixture, the upper part of the upper fixture is connected with the upper beam, the lower part of the upper fixture is provided with two lower loading pressure heads arranged left and right at an interval, the lower part of the lower fixture is connected with the lower beam, the upper part of the lower fixture is provided with an upper loading pressure head, and an installation space for installation of the test sample is formed between the upper loading pressure head and the lower loading pressure heads. When in test, the part of the fixture component, which is used for clamping the test sample, can be placed into a hearth of the heating furnace through adjustment of the positions of the upper fixture and the lower fixture, so that the test sample is heated. The test system can be used for measuring the bending characteristic of the test sample under high temperature environment and analyzing the stress relaxation behavior in a three-point bending state.