In order to study the early age cracking of zero block concrete due to heat of hydration, a three-dimensional finite element model was established based on the secondary development of ABAQUS for the zero block of the Peisen Liujiang Special Bridge in Guangxi Province, and the effects of hydrating model and the number of pouring operations on the concrete temperature and maximum principal stress were investigated. The simulation results show that: layered casting reduces the peak concrete temperature by 11.8% compared to one casting; The hyperbolic and composite exponential models can reduce the peak concrete temperature by 13.7% and 10.8% respectively compared to the exponential model the maximum location of the first principal stress appears at the interface between old and new concrete, taking into account the effects of early age modulus and tensile strength. The first principal stress is reduced by 2%, 36.7% and 39.8% respectively at the intersection of old and new concrete, at the centre web leading angle and at the manhole leading angle compared to the single pouring method; There is an approximately linear relationship between the peak first principal stress and the heat of hydration at the intersection of the old and new concrete and the centre web guide angle, taking into account the effects of different hydration models.