In order to study the influence of steam curing on high volume concrete box girder, combined with high temperature steam curing precast concrete box girder project of a Yangtze River Bridge, the temperature and strain sensors were embedded in the 30 m box girder, and the temperature and strain changes of box girder during steam curing and later curing were obtained. The results show that the average temperature of test section is lower than mold temperature after 66 h. The hydration heat of concrete reaches the peak value at 11~13 h, and the peak temperature of measuring points in each area of the section from large to small is the junction of top web plate, the top plate, the web plate, the bottom plate and the junction of bottom web plate. The peak temperature at the junction of top web plate and top plate is higher than that in other areas. The maximum temperature difference between interior and surface, and between surface and exterior of box girder is 18.62 and 14.29 ℃, respectively, both of which appear before steam curing. During the whole curing process, the tensile stress generated inside the box girder is less than splitting tensile strength of concrete, and there is no risk of cracking in girder. After the tension of prestressed steel beam is completed, the strain of each test section is compressive strain, and the later change range is not large.