This paper presents a dynamic thermal tensioning method to control the welding induced distortion under production variation. The new method determines the optimal thermal tensioning parameters based on real-time distortion measurements. The paper is focused on a systematic study on the structural response and the development of an automatic control algorithm for the dynamic thermal tensioning process. A thermomechanical finite element model was used to study preheating effects in a gas metal arc welding process. A model predictive strategy was adopted for automatic distortion control. It has been found that the response of the dynamic thermal tensioning process is nonlinear and time varying. However, the response model can be linearized based on the superposition principle. A threshold-based control algorithm is developed and demonstrated using both simulation and experimental results.