The invention relates to a rotary double-station positioning machine for welding. The rotary double-station positioning machine for welding comprises a U-shaped support and supporting shafts, wherein the supporting shafts are fixed on the upper part and the lower part of the U-shaped support; axes of the supporting shafts are superposed; a lifting ring which are matched with the two supporting shafts through bearings respectively is arranged in a U-shaped recess formed in the U-shaped support; a motor, a speed reducer and a driving gear are mounted at the bottom of the lifting ring; the speed reducer is fixed on the motor; the driving gear is mounted on the speed reducer; a driven gear which is engaged with the driving gear is arranged on the upper part of the lower supporting shaft; a supporting table is mounted at the upper end of the upper supporting shaft; and a two-degree-of-freedom adjusting device is mounted at the upper end of the supporting table and is in sliding fit with the lifting ring. The rotary double-station positioning machine for welding has the advantages of reasonable structural design, high automation degree, high control precision and the like. Free switching of double stations in a welding process is realized, a two-degree-of-freedom position adjusting function is fulfilled, and therefore, requirements of welding of different workpieces are met.