Thermal PreStressing Method(TPSM) is a new design and construction concept for prestressing various types of steel and concrete structures. A new retrofitting method for steel-concrete composite bridge is developed through this study, which is a hybrid method of external post-tensioning and thermal prestressing, combining the merits of the two methods. The proposed method is founded on a simple concept of thermal expansion and contraction of steel. An external prestressing plate, used as a post-tensioning retrofitting device in this method is heated by electric heaters before it is attached to the bridge. When attached using high tension bolts at several points, the heaters are removed, the contraction force of the steel plate applies eccentric axial forces to the section of girder. This paper describes the basic concepts of TPSM, its verification by a parametric study that analyze the effect of Thermal Prestressing Method for steel-concrete composite bridge.