Abstract: According to the service environment of the platform along Lanzhou Metro Line, coupled salt solutions containing SO₄²⁻, Cl⁻ and Mg²⁺ were allocated. The reinforced concrete specimens were placed in a coupled salt solution for nondestructive testing every 90 days. Weibull distribution model was selected. Fixed and dynamic parameter estimates of the degradation distribution were obtained by least square method and BLUE method. The results show that the corrosion ions in coupled salt solution reach the surface of steel bar by diffusion, permeation and electrochemical migration. The pH value near the steel bar decreases, and the passivation film transits from undamaged state to partial damaged state. The polarization curve moves towards the direction of negative potential and increasing corrosion current density, and the AC impedance graph shows a double capacitive reactance arc, while the low-frequency impedance arc radius gradually decreases and contracts to the real part of the impedance. The reliability curves show three-stage variation characteristics. Among the dynamic parameter estimates, the reliability life of the cubic scale parameter is the closest to that of the fixed parameter value, the failure rate is the largest, the reliability life of the exponential scale parameter is the shortest, the failure rate is the smallest, the power type is between the two, and the dynamic parameter function must be between them. The first derivative and the value of the function must be positive. Otherwise, the result of the reliability calculation is complex. The influence of the scale parameter function form on reliability curve is greater than that of the shape parameter function form on reliability curve. When the scale parameter function type is fixed, the shape parameter function type has great influence on the life result. However, the reliability curve changes obviously with the scale parameter function type altering.