A new three-dimensional deformation measurement method was proposed based on digital image correlation and binocular stereovision to measure the full-field deformation in metal sheet welding processes. Firstly, an algorithm based on a seed point was proposed to provide a reliable initial value for the least-square nonlinear optimization in the correlation matching. Then, the algorithms for three-dimensional coordinate reconstruction, three-dimensional displacement and the strain calculation were discussed separately. Finally, based on these algorithms and the VC++6.0 platform, a welding deformation measurement system was developed for the full-field deformation of metal sheet welding. With self-developed image acquisition devices and a standard material testing machine, a steel standard tensile test and a welding deformation measurement test were conducted to validate the performance of proposed mthod. Experimental results demonstrate that the accuracy of strain measurement is not lower than 0.5%, which is very close to that of a extensometer and the measured 3-D displacement time history is reasonable. It concludes that the proposed method can satisfy the requirements of non-contact, higher precision, and it is a more intuitive way for full-field deformation measurement during metal sheet welding processes.