Thermal properties of concrete core cooling slab have direct and strong influence on its dynamic cooling performance. Star-type RC-network model can be used to simulate thermal dynamic performance of concrete cooling slab, but the heat resistance and the heat capacity of assumed core temperature layer in the model is difficult to determine. This article proposed a method to define these two thermal properties in geometric way, and modified RC-network model was established in order to validate the method. Then thermal steady and dynamic performances of two typical concrete core cooling slabs were simulated by the modified star-type RC-network model and FEM respectively. The results indicate that the modified RC-network model was in good agreement with FEM both in dynamic and steady cooling performance simulation. Furthermore, application scope of the modified RC-network model was investigated and defined. (C) 2011 Elsevier B.V. All rights reserved.