Abstract: Thermal fatigue crack problems of the feedwater nozzle for steam generator have attracted widely attentions, but haven't yet been fully resolved. Depending on the application characteristics of finite element analysis, we developed finite element software ATLAS by directly programming to hardware with OpenGL graphics engine VBO, FBO and GLSL technologies. By fully using of three-dimensional rendering capabilities of the GPU, ATLAS provided a large-scale highly interactive visualization environment for engineers. ATLAS was used to simulate the thermal stress of the feedwater nozzle. A simplified model of the nozzle finite element analysis was created, and the loads and temperature boundary conditions of the nozzle were added on the interior surfaces. The thermal stress curve was obtained after conducting structural thermal stress analysis. We found that ATLAS can accurately import CAD models, mesh, apply a variety of conditions, and complete the numerical simulation of the thermal stress of the nozzle. ATLAS results were consistent with those of ABAQUS calculation, so its accuracy was assured. Finally, we validated the results and draw conclusions.