<p>Multi-pass high-speed friction stir processing (FSP) was used to process a 2&#xa0;mm thick Al-Mg-Si alloy sheet. The influence of processing passes on macroscopic forming characteristics, microstructure evolution and tensile properties of processed zone were considered. The microstructure is significantly changed subjected to multi-pass high speed FSP. The recrystallization mechanism of processed zone is continuous dynamic recrystallization (CDRX) and geometric dynamic recrystallization (GDRX). Except for slight coarsening of precipitates, the mean grain size in the processed zone is significantly refined. As increasing processing passes, the average grain size becomes smaller. As a result, the elongation of the processed zone is significantly enhanced, reaching a maximum of 44.3%, but the tensile strength decreased to some extent compared to the Al-Mg-Si alloy.</p>