Abstract: In this paper, the high-speed camera and welding electrical signal collection system were applied to observe the metal transfer of CMT + P welding process in SAF2507 Super Duplex Stainless Steel. The metal transfer behaviors, change of waveforms and heat input characteristics with different WFS of CMT and CMT + P were analyzed. The droplet transfer characteristics were revealed. The results show that there are many differences between the actual waveforms and the theoretical waveforms. The shape and size of the droplet, transfer form, the wave state of molten pool, the distance from the wire tip to the workpiece and the spatter can all affect the fluctuation of the voltage. The voltage waveform diagram can be used to guide the analysis of the metal transfer behaviors. The pulse period plays a major role in heat input, and the control of heat input can be realized by adjusting pulse peak current, pulse base current and the number of pulses.