Taking 10 mm thick polypropylene (PP) plastic as the research subject, friction stir welding technology was used to connect it, and the influence of processing parameters on the macro morphology and mechanical properties of PP plastic was explored. The results showed that when the rotation speed was 600~1 000 r/mim, the forward speed was 70 mm/min, and the pressure was 0.1 mm, there was no obvious defect on the welded forming surface. With the increase of rotation speed, the tensile strength initially increased significantly, reaching a maximum of 22.05 MPa at 800 r/mim, which was 71% of the base material, and then decreased. The base material tensile specimen exhibited ductile fracture, accompanied by the formation of a fine neck and localized grain fibrillation, whereas the connected specimen showed brittle fracture. With the increase of rotation speed, the average friction coefficient decreased slowly at first and then significantly. At the rotation speed of 800 r/mim, the average friction coefficient reached the minimum of 0.338 and then increasesd significantly. The wear form of the base material and the connected specimen surface was mainly plastic wear.