Abstract: The regenerator in the outlet of a reheating furnace was studied. A one-dimensional unsteady state model was set up, and discretization was gotten through finite difference method. A program of computing the heat saturating time of the solid sphere regenerator was developed by C++ language. The relationship between the heat saturating time and the factors which influence the time was determined. It is shown that the heat saturating time decreases when the heat convection coefficient increases; whereas the increase of heat capacity, density and diameter of regenerator make the heat saturating time increase linearly.