Abstract: No matter what method one uses to the unsteadytemperature field calculation of massive concrete forward difference method, centraldifference method or backward difference method, the error of temperatureis inevitable. Based on Lagrange mean-value theorem and the uncouplingassumption of temperature difference and temperature change rate among allnodal points, an iterative algorithm is put forward, which proves to be aneffective method for temperature field calculation of massive concrete. Bythis method, the calculation cost is decreased and at the same time, the solutionprecision can be under control when the time step is properly increased.On the other hand, if the time step is kept in a conventional level, the calculationcost is increased slightly, yet the solution precision can be greatlyincreased, and the numerical calculated results may approach the theoreticalresults.