Abstract: Porosity is apt to occur in deep penetration laser beam welding, which has severe influence on the mechanical properties of laser welded joint. In this paper, repression of porosity with beam weaving laser welding was investigated. Considering Ar and N₂ porosities which may appear during laser welding, welding experiments were carried out by using a 3 kW high power laser. The results indicate that beam-weaving laser welding can remarkably reduce N₂ porosity with weaving frequency increasing, and porosity can be eliminated when weaving amplitude is only 0.5 mm. Beam-weaving laser welding can also effectively reduce Ar porosity. Ar porosity in weld metal is decreased with increasing weaving frequency and amplitude.