The invention discloses a waveguide junction circulator power test method with the low power source demand, and belongs to the technical field of microwave components. The waveguide junction circulator power test method comprises the following steps that a half-cavity structure waveguide junction circulator is made; adapters are made; the three adapters are adopted to be assembled with the half-cavity structure waveguide junction circulator together to form a half-cavity structure test sample; and according to the requirements of a power test, the obtained half-cavity structure test sample isconnected into a power system in the corresponding transmission direction, and the loaded power is about half of the loaded power of a complete structure waveguide junction circulator. Through the waveguide junction circulator power test method, the problems that an average power test and limit power evaluation cannot be carried out due to the lack of a power source of the waveguide junction circulator can be solved; and meanwhile the demands of a waveguide junction circulator power test and a limit power evaluation test for the power source can further be lowered, the test cost is lowered, the harm of the power system to testers is reduced, and protection to the power test system is improved.