Temperature effect is one of the main factors that influence the performance of box girder-track in high speed railway. Through the continuous temperature field monitoring of CRTS I twin-block ballastless track with 32 m simple supported beam bridge for the entire year,the time-dependent temperature variation and the regular distribution of temperature gradient were analyzed. The representative values of temperature differences with a certain return period were ascertained by Higher Moment Method. Based on the 16560 data at each measurement point,the vertical temperature load modes of box girder-track in southeastern China were suggested. The analysis results reveal that the goodness-of-fit is increased by using the first Fourier series to simulate the temperature fluctuation characteristics of sunny day,and the same season fitting parameters a,b,ω and φ decrease from top to bottom and the temperature fluctuation amplitude of a is close to 0℃ as the depth increases. The diurnal variation characteristics of each section on sunny days are basically similar in the different seasons,and the positive and negative temperature gradients approximately appear around 11:00 to 21:00 and 01:00 to 9:00,respectively. The positive and negative representative values of box girder-track vertically are 14.87℃ and -6.3℃ with the exceedance probability of 0.01,respectively. And the positive and negative representative values of the top plate and bottom plate are 13.74℃,-3.54℃ and 2.38℃,-1.12℃ with the exceedance probability of 0.01,respectively. The values of positive and negative temperature difference of top plate are fitted by the exponential form,which is approached to the temperature load modes of the concrete box girder in Chinese railway bridge code. The values of bottom plate are fitted by linear form. The correlation coefficients of the two fitting forms are more than 0.99,which can be used for the engineering application and reference.