Abstract: 2219 aluminium alloy with 5 mm thickness was used as the experimental material, the metal transfer and bead formation characteristics of aluminum alloy welding under different pulse laser-arc arrangement (i.e. different laser incident points) were studied, and the mechanism for the increase of weld penetration was analyzed. The results show that when the pulse laser irradiates the base material, it mainly provides heat input to the base metal, and the temperature increase of the base material helps to promote the droplet spread and stabilize the metal transfer process; when the pulse laser illuminates the solid-liquid interface of the droplet, it primarily provides a recoil force to the droplet. A stable "one pulse per droplet" transfer is obtained, which significantly increases metal transfer frequency and the droplet flight speed. The welding penetration is enhanced by the increase of droplet impact force on the molten pool. When the pulsed laser alternately illuminated the molten pool and the droplet, on the one hand, the base material can be heated to facilitate the spreading of the droplet, and on the other hand, the metal transfer frequency and the uniformity of the bead formation can be improved.