Abstract: To study the influence of different welding processes on the residual deformation of flexural steel beams under load, we carried out welding strengthening test of four Q345B I-shaped bending steel members under load. The welding processes of the four steel beams are designed considering engineering applications. The changes of the mid-span deflection of the steel beams and the lateral deflection of the upper and lower mid-span flanges during the whole welding process were measured. This paper explains some special problems and test phenomena in the test, analyzes the influence of the welding processes on the mid-span residual deflection and mid-span rotation angle, and compares the calculated and experimental values of the welding residual deflection. The aims are to provide experience in conducting welding reinforcement test, to better understand the influence of welding process on the development of welding residual deformation, and to provide experimental basis and suggestions for the test design and design methods of welded steel beams under load.