“Under freeze-thaw conditions, the compressive strength of RC structures in service in Harbin and Jilin regions exhibits multi age degradation characteristics. By combining ultrasonic rebound comprehensive method with core sampling correction test, the on-site measured data were normalized and merged. Non parametric testing was used to determine the probability distribution function of concrete strength over time, and regression analysis was conducted on the correlation between relevant parameters and service life. The research results indicate that the time-varying model of the core drilling method modified by the ultrasound rebound comprehensive method follows a linear variation law; The relative compressive strength of concrete at different service ages follows a normal distribution; The variation of the mean and standard deviation of the relative compressive strength of concrete with service life can be characterized by quadratic polynomial models and linear models, respectively.”