Abstract: For its good mechanical properties and weld ability,low carbon structural steel is widely used in a variety of welded structure.The angular distortion is a serious problem to be resolved in the butt joint welding process.The angle distortion changes in multiplayer welding butt joint of Q235 low carbon steel plate are measured,and the angle changing process and characteristics of deformation of the joint are analyzed and summarized.The results show that linear variation in volume with temperature variation has an effect on angular distortion.In addition,high-temperature phase transformation above 700℃ will affect the angular distortion of single-layer weld and the root weld of multi-layer and multi-pass welding but has less effect on that of the multi-layer welding except the root weld of multi-layer welding.