The invention discloses a staggered spoke type stretchable tool for friction stir welding. The staggered spoke type stretchable tool comprises a bearing, a bearing sleeve, a first supporting ring, a second supporting ring, a third supporting ring and a plurality of supporting plates, the bearing is used for connecting the spoke type tool with a cross-shaped operation machine type dislodgement machine, the bearing sleeve is rotationally arranged on the bearing in a sleeving manner, the first supporting ring is annular, an inner ring fixing sleeve is arranged on the bearing sleeve and can rotatealong with the bearing sleeve, the multiple first air cylinder assemblies are arranged on the outer ring of the first supporting ring and distributed on the outer side of the first supporting ring ina circumferential array equal-interval manner, the second supporting ring is annular, is concentric with the first supporting ring and is arranged on the outer side of the first supporting ring, a plurality of round holes are formed in the second supporting ring, air cylinders can penetrate the round holes, the supporting plates are arc-shaped plates, and the first air cylinder assemblies can bedetached to be far away from one end of the third supporting ring. The invention further discloses an adjusting method of the staggered spoke type stretchable tool for friction stir welding.