The invention provides a magnesium-aluminum double-layer composite barrel-shaped part and a staggered-distance spin forming process thereof, and belongs to the technical field of composite barrel-shaped part forming and spin processing. The staggered-distance spin forming process comprises the following steps of: machining to obtain an aluminum alloy outer barrel and a magnesium alloy inner barrel; grinding and cleaning the aluminum alloy outer barrel and the magnesium alloy inner barrel; and performing staggered-distance spin forming on the aluminum alloy outer barrel and the aluminum alloy inner barrel. The magnesium-aluminum double-layer composite barrel-shaped part is manufactured through a staggered-distance spin forming technology, and the composite barrel-shaped part takes the aluminum alloy as an outer-layer material to improve plasticity and corrosion resistance of the barrel-shaped part; and meanwhile, the great advantage of being light of the barrel-shaped part is kept.