To investigate the distribution of temperature field of the main underground structure under the coupling effect of hydration heat and ambient temperature，the FEA finite element software was used to simulate the temperature field based on the underpass reconstruction project of the Gongchang road at the position of the Shenzhen campus of the Sun Yan-sen University. The automatic monitoring data of the internal and external temperature field of floor concrete of main structure was analyzed and compared under different construction ambient temperatures. The results show that the temperature difference of hydration heat of mass concrete can be effectively control at a suitable construction ambient temperature. Effective heat preservation measures need to be taken to prevent temperature cracks，when the ambient temperature of construction is low. In the case of large variation in the construction ambient temperature，cement with low heat of hydration should be selected.