In this paper, 5wt.% Al3Zr/aluminum matrix composites are taken as the research object, plasma welding with Ar gas as ion gas and Al-Ti-B as wire material. The corrosion polarization curve of weld area in 3.5% NaCl solution is measured by electrochemical comprehensive tester. Scanning Electron Microscope (SEM), X Ray Diffraction analyzer (XRD) are used to analyse and characterize the microstructure and phase composition of the composite and its weld.The corrosion behavior and corrosion mechanism of Al3Zr/aluminum matrix composites after plasma welding were studied in 3.5% NaCl solution. The SEM analysis results show that through plasma arc welding, a better weld can be obtained, and the weld microstructure is mainly composed of Al3Ti phase and Al matrix, and the Al3Ti phase is striped and spherical. The electrochemical polarization curves indicate that the corrosion resistance of the materials at the nugget is slightly lower than that of the base metal.The weld of composition corrosion mechanism immersion is that the Al3Ti phase and the matrix phase behave as the anode and cathode of a primary cell.