Abstract: Ambient temperature，sunshine duration，and solar radiation intensity are three important parameters af-fecting the vertical temperature gradient of the concrete box girder． However，the current code temperature gradient model does not consider the significant differences in environmental and thermodynamic parameters between re-gions． In order to accurately reflect the differences in temperature patterns across regions in China，the representa-tive cities of typical climate regions were selected． Based on real-time shadow technology，the thermodynamic ana-lysis model of concrete pavement and asphalt concrete pavement concrete box girder was established by ANSYS，and the real-time temperature field and vertical temperature gradient of the concrete box girder were studied． The study shows that the maximum vertical temperature gradient value of the concrete box girder appears in Xi'an，and its vertical temperature gradient curve can be fitted by exponential function and straight line． The distribution of vertical temperature gradient in China's current highway code differs from that of actual temperature gradient to some extent． In the code，the temperature gradient at the top of box beams using concrete paving is too large，and the temperature gradient at the top of box beams using asphalt concrete paving is too small． As compared with the con-crete pavement，the 9 cm-thickness asphalt concrete pavement can reduce the upper limit value of the maximum vertical positive temperature gradient of the box girder by 4 ℃，the lower limit value by 3 ℃ and the occurrence time by two hours．

Key words: concrete box girder, thermodynamic analysis, real-time shadow technology, vertical temperature gradient, distribution law