An ES/ONS-FEM numerical simulation method is proposed in this study, combining the edge-based smoothed finite element method (ES-FEM) and the optimized node-based smoothed finite element method (ONS-FEM) for thermo-elastic coupling analysis based on linear tetrahedron elements. Prior to thermal stress analysis, the temperature field was analyzed using ES-FEM to obtain a high-accuracy temperature field, followed by thermal expansion using ONS-FEM. This method approximates each subdomain of the smooth domain as a sphere and selects the integral points required for optimization on the sphere surface. The optimization term of the node-based smoothed finite element method (NS-FEM) is generated from these integral points. ES/ONS-FEM retains the high accuracy of ES-FEM and the relatively inflexible stiffness matrix of ONS-FEM, resulting in accurate results. The results that ES/ONS-FEM takes more time than FEM but the error is much smaller than FEM and NS-FEM, can be illustrated by three examples. Among them, the lowest relative error of ES/ONS-FEM is only 0.0139. The results show that ES/ONS-FEM modifies the defects of NS-FEM and enhances the dominance of nodal integration. The effectiveness of the presented formulation in dissolving thermo-elastic substances was evaluated objectively and accurately.