Abstract: The defects in 2A14 aluminum alloy electron beam welded (EBW) joints were studied. Their appearance features and formation causes were analyzed,and controlling methods were proposed for helping to improve the quality of the joints. The results show that the crack in 2A14 aluminum alloy EBW joint was solidification crack,which could be diminished by increasing scanning frequency of electrode beam in order to reduce the composition segregation and refine the grains. Porosity could be reduced by cleaning the oxide film,increasing scanning frequency and properly re-melting. Shrinkage cavity could also be improved by increasing scanning frequency and re-melting. Excessive penetration could be eliminated by changing welding structure,and softened zone in welded joint disappeared after post-weld heat treatment.