Abstract: The test system which consists of welding system, high-speed camera system and synchronous waveform information acquisition equipment was built. The effects of different pulse waveform parameters on the droplet transfer, weld formation and porosity in pulsed MIG welding of 6061 aluminum alloy were studied. The results show that under the condition of average current of 200 A and 300 A, compared with the standard pulse waveform of one-pulse-one-drop transition form, the droplet transition changes into a mixed transition form of droplet+jet by increasing the peak time of pulse waveform and reducing the pulse frequency, and the impact strength and duration of the liquid column on the molten pool increase, which can significantly increase the weld penetration. The weld penetration at 200 A and 300 A is 16.2% and 38.8%higher than that of one-pulse-one-drop transition, respectively. In addition, in the mixed transition mode, the gas in the molten pool is more likely to escape due to the impact and oscillation of molten droplets on the molten pool, and the porosity is relatively reduced.