Abstract: The electrochemical behavior of Alloy 690 in primary circuit simulated solutions was investigated by potentiodynamic polarization,electrochemical impedance spectroscopy(EIS),dynamic electrochemical impedance spectroscopy(DEIS) and capacitance measurements.It is shown that Alloy 690 has a narrow passive anodic region in the test solutions.But the second passive phenomenon is found at the 0.5 V potential.EIS results indicate that the impedance value of the passive film in the solution without Cl^- anions is higher than that in the solution containing Cl^- anions.DEIS results demonstrate that the transfer trend of the passive films with increasing potential in both the test solutions is similar.The results of DEIS measurements are in agreement with the potentiodynamic polarization curve well.Mott-Schottky analysis of the passive film formed on Alloy 690 at the 0.2 V potential presents that the donor density and the acceptor density become larger with the addition of Cl^-.