Abstract: A 0.1mm copper foil was embeded in the transverse direction of T-joint as marker material by corner stationary shoulder friction stir welding. After welding, X-ray 2D transmission and X-ray 3D scanning were carried out on the corner weld of T-joint. 2D and 3D flow fields of the marker material of corner weld were obtained. Friction shear was dominant effect in the thermoplastic material of the advancing side. Material flow was mainly along the direction of welding, and flows through the retreating side to the advancing side. Material of the retreating side was mainly extruded. Due to the T-joint pin threads, the material flowed backward and downward as a whole. At the same time, it was found that there was an "accumulation area" of marker material at the adjacent rear of the stationary shoulder. According to the observed results, the main three-dimensional flow characteristic model of T-joint corner weld was established.