The work aims to investigate the effects of vacuum degree on pitting of 2205 duplex stainless steels in seawater desalination environment. Pitting and repassivation behavior of the 2205 duplex stainless steels was studied in electrochemical methods including cyclic anodic polarization curve and electrochemical impedance spectroscopy (EIS) in 1.5× artificial concentrated seawater, corrosion morphology of polarized testpieces was analyzed with scanning electron microscope. Cyclic anodic polarization curves and electrochemical impedance spectra of the 2205 duplex stainless steels were tested in seven different vacuum states. It was found that self-corrosion potential(vs.SCE) of the testpieces decreased from -256 mV to -485 mV, pitting potential(vs. SCE) decreased from 605 mV down to 363 mV, and pitting tendency increased significantly as vacuum degree increased. Semicircle in Nyquist curve gradually became flat and phase angle in Bode plot decreased from 80° to 77°, while difference between the pitting potential and passivation potential gradually increased. Morphology of pits on the surface of testpieces was not exactly same after cyclic anodic polarization in different vacuum degree, and number of pits increased obviously with the vacuum degree increased. When the vacuum increased to 0.72, size of pits decreased significantly. As the vacuum degree increases gradually, compactness and protectiveness of passive film on stainless steel decrease, electrochemical impedance value decreases gradually, pitting corrosion resistance became worse, while repassivation performance increases and corrosion degree of the testpieces decreases after cyclic anodic polarization.