Abstract: The stability of high power single beam laser and double beam laser welding process of aluminum alloy was studied from the aspects of the appearance of weld, porosity, fluctuation of penetration, keyhole, plasma, spatter and so on. The experimental results show that, under the same process parameters, the surface of the double beam laser welding is obviously better than that of the single beam, and the fluctuation of the penetration is smaller than that of the single beam. Under the same process parameters and the same depth of penetration condition, compared to single beam, double beam weld porosity rate is lower ,the keyhole and plasma fluctuation cycle is longer, coefficient of variation of keyhole orifice area is smaller, spatters is finer and more uniform.