Experiments of dual-beam CO2 laser welding aluminum alloys were conducted. The weld appearance, porosity content and joint strength with parallel and serial dual-beam laser welding were investigated. CCD and CMOS image sensors were respectively used to monitor the metal pool and plasma from both paraxial and coaxial directions. The results in above aspects of single-beam and dual-beam welding were simultaneously compared. The results indicate that dual-beam laser welding aluminum alloys can reduce the size and therefore increase the stability of plasma in comparison with single-beam laser welding, which usually results in better weld shaping. A comprehensive comparative analysis on the parallel and serial dual-beam welding shows that the former is more favorable in weld shaping, but it will decrease the penetration in some degree.