Abstract: Electrochemical studies are performed to investigate the corrosion resistance of uranium niobium alloy before and after passivated with carbon monoxide.Using X ray photoelectron spectroscopy (XPS), the surface composition of specimen passivated with carbon monoxide is determined.The corrosion resistance of uranium niobium alloy is well improved because the passive layer (UC/UC x O y +Nb 2O 5+UO 2) on surface serves as passive film and increases the anodic impedance after the specimen is passivated with carbon monoxide.