To investigate the temporal–spatial temperature field and mechanical response of an orthotropic steel bridge deck during paving with gussasphalt concrete (GAC), in situ monitoring of the Cuntan Yangtze River Bridge in China was conducted during GAC paving, and a finite element method model of the temperature field was established. The test and model show the following: (1) The maximum temperature occur at the paving area mid-span on the steel bridge deck, and the temperature stress of the ribs is non-negligible. (2) The deck in the paving and non-paving areas is mainly subjected to compressive and tensile stresses, respectively. (3) The beam end of the steel box expanded outward, and the deck bulge upward. (4) Based on the analysis of the construction parameters, the paving temperature and width have a greater influence than the paving speed on the stress and deformation fields. In bridge design, the temperature-stress problem caused by high-temperature pavement and the pavement thickness problem caused by the temperature deformation of the deck must be considered. The longitudinal elongation should meet the allowable limits of the corresponding telescopic device. These results can provide a reference for construction workers and maintenance personnel of bridge deck pavement.