For getting temperature distribution property in steel box girder,25 temperature sensors were planted along bottom of bridge deck transversely and diaphragm vertically in a certain Changjiang bridge,so temperature of steel box girder’s crucial components were tested while Gussasphalt mixture paving.Basing on datum analysis and simulation,the worst temperature gradient was got,and formula for predicting the maximum temperature of the bottom of steel deck was created. Result shows the maximum temperature under steel deck and the maximum rise extent of temperature can reach 84℃ and 67℃ respectively.Temperature can rise at 0.83℃/min averagely and 2.10℃/min in special period.The influence range of paving temperature is 1.2m around paving area,and the worst transverse and longitudinal temperature gradient is 58℃/m和10℃/m respectively.Vertical temperature gradient can be simulated with exponent function.The maximum temperature under steel deck can be predicted with air temperature,paving temperature and thickness of mixture.It is concluded that relative high temperature gradient occurs in local area of steel box girder when asphalt pavement is to be paved at high temperature,and which can supply reference for thermal stress analysis.