Due to the characteristics of light weight and high strength,2 A12-T42 aluminum alloy has been used as the main materials of aircraft. Refill friction stir spot welding（RFSSW）as a novel solid phase connection technology,was carried out to investigate the joint,the appearance and microstructure were analyzed by SM and metallographic microscope respectively,the corrosion behaviour of RFSSW joint was investigated by immersion test,static weight loss test and polarization curve test. The experiment results show that the RFSSW joint has a good forming and defect-free on the surface,the metal microstructure and precipitate phase of joint is differentiated in different districts,the grains of SAZ and PAZ are small as the direct stir with the tool,the metal microstructure and precipitate phase of TMAZ is distributed in a certain direction,for the affection of heat input in HAZ,the microstructure grain grew and the precipitate phase coarsed and aggregated. Immersion test shows that the corrosion resistance of 2 A12-T42 RFSSW joint is differentiated in different districts,the corrosion resistance of HAZ is the lowest,and the pitting corrosion is developed firstly,the corrosion resistance of SAZ is the highest. The corrosion resistance of RFSSW joint is lower than that of base metal. The polarization curve test shows that the sequence of the corrosion resistance in each district from high to low was SAZ,PAZ,BM,HAZ/TMAZ.