For the laser-MIG hybrid welding process of A7 N01 aluminium alloy,the change rules of electrical parameters under different protective atmosphere and the influence of protective gas composition on metal transfer period are studied. In the experiment,different proportions of helium-argon mixed shielded gas are used to collect the electrical parameters of A7 N01 aluminum alloy during welding process and to calculate the metal transfer period. The effects of different proportions of helium-argon mixed shielded gases on weld formation and pore defects are studied. The results show that the regularity of electrical parameters is strong and stable when the proportion of argon in mixed atmosphere is high;with the appearance of short circuit voltage,the electrical parameters of welding process are no longer periodic when the proportion of helium is more than 50%. The higher the proportion of helium,the longer the metal transfer period;when the proportion of helium exceeds 50%,the quality of weld formation decreases,and overlap and spatters occur;the addition of helium will improve the inevitable blowhole phenomenon in high purity argon atmosphere and reduce the porosity and blowhole size.