The Passive Intermodulation(PIM) value of the reflector's metal mesh, an important performance parameter of high-power spaceborne mesh antenna, is tested traditionally by the radiation method which requires a large size of metal mesh sample and has a low test efficiency. A 3-port PIM test method is proposed for the metal mesh, which is carried out by adopting a waveguide testing system based on the 3-port module. A PIM performance test system based on the 3-port module is constructed in order to verify the effectiveness of this test method. The PIM performance test is carried out on two metal mesh samples of the traditional type and the improved type, respectively. The test results show that the PIM performance of the improved metal mesh sample has been improved by 50 dB than that of the traditional mesh sample. This metal mesh's PIM test system bears the characteristics of high integration, stable performance, and high system construction efficiency. The test sample size for the proposed method is reduced to about 1/10 than that of the traditional method. The proposed 3-port PIM test method provides support for the rapid research of novel low-PIM-level metal meshes.cuizhen3@126.com.