Temperature is one of the important reasons causing the cracks on the bridge structure during the construction and operation. In this paper, the temperature field produced by hydration heat and early thermal stress of a 64 m simply supported channel-box girder are simulated during casting process, considering the time-varying characteristics of concrete shrinkage and creep, elastic modulus, and tensile strength. Then, various parameters influencing the temperature field are analyzed, and the corresponding measures of controlling temperature cracks are proposed.