In this study, multi-pass spinning of AZ91 magnesium alloy tube was conducted by power forward spinning. The microstructural evolution, phaseStransformation and micro mechanical properties were examined by opticalSmicroscope, SEM-EBSD-EDS, and nano-indentation tests. The results show that when the wall thickness of AZ91 magnesium alloy tube reduced by 88.33%, the surface was well formed without cracks or folds. In the initial stage of spinning, plastic deformation mainly occurred on the outer surface of magnesium alloy. With the spinning deformation increased, the deformation of inner and outer surface tended to be consistent. The brittle phase Mg₁₇Al₁₂ broke down and distributed with a streamline shape in magnesium alloy. At the same time, the grain of magnesium alloy refined and dynamic recrystallization occurred. With the increase of deformation, the strength of tubular parts increased, and the hardness was up to 1.036 GPa. The strengthening modes mainly include second phase dispersion strengthening and fine grain strengthening.