This paper develops mathematical model for the flat plate which is including temperature dynamics of the top surface on the plate TPi(t) and dynamics of the heat load through the plate Q(t), both depending on the air temperature changes Tao(t) on one side and Tai(t) on the other side of the plate. The method of system dynamics, known as Forrester's dynamics, was used for development of dynamic model. Model is based on concentrated parameters and therefore simple differential equations are used for description of the plate temperature dynamics. Powersim program is used for simulation. Evaluation of dynamic model is performed for the plate edges with different values of the Biot number. Comparison of the simulation results and analytical computation is presented in a form of a table. It is confirmed that simulation model follows trend of the temperature dynamic on the top surface of the plate. Presented model is adequate both for thermally-thick and thermally-thin plates.