Thermal sensors have been installed on a curved bridge of high-speed rail.By means of carrying out 2 years monitor of CRTS II ballastless track，the time-varing rules are revealed.Through daily temperature data calculated from the measured data by using difference method of time series，the time-varing curve of uniform temperature，which represents the trend of bulk temperature change laws，can be obtained.Then，the rules of track temperature variance with atmospheric temperature are effectively reflected.In order to examine the change law of uniform temperature，Fourier curve fitting and high-moment statistical model are utilized，and the overall curve representing the changing laws of track temperature are put forward.The results show that the track uniform temperature appeared trigonometric development with a tropical year (namely 365 days) as a cycle，and the regression parameters can represent its median，amplitude and phase-difference.The entire section of the track can be analyzed as a whole，because the fitting results among test points are close，which indicates that the changing laws of track uniform temperature can be expressed by its overall curve.By using high-moment statistical model to analyze the differences between overall curve and its fitting curve，the representative value of overall curve with probabilistic guarantee can be obtained.