The effects of different Cl- concentrations on the corrosion behavior of pure zirconium and its welded joint were studied by electrochemical test and numerical fitting, and the mechanism was discussed. The results showed that:In the solution containing Cl-, the potentiodynamic polarization curves of industrial pure zirconium base metal and its welded joint show certain passivation behavior, and with the increase of Cl- concentration, the corrosion tendency of the base metal and welded joint increases, the potentiodynamic polarization curves move to the lower right, the polarization resistance of the material decreases, the corrosion current density increases, and the corrosion resistance deteriorates. Compared with the base metal, the corrosion current of the welded joint is larger and the pitting potential is lower under the same Cl- concentration, and the difference in microstructure is the main reason for the poor corrosion resistance.