A numerical model has been constructed based on the solution of the magnetohydrodynamic equations within the framework of phase field algorithm to simulate the metal transfer process and to investigate the effect of power source dynamics on metal transfer and heat transfer behaviors in pulsed gas metal arc welding. Three typical kinds of power source dynamics (i.e. exponential, ideal square and trapezoidal waveform) using identical nominal pulsing parameters are considered and compared. The ideal square waveform with infinitely steep-sided pulse would lead to a higher detaching speed and an earlier detachment than other waveforms. Decrease in the response rate of the power source shows a retarding effect on the dynamic characteristics of the metal transfer, leading to a delay of detachment and a lower detaching speed. Moreover, this retarding effect is more and more significant as the response rate decreased and may even alter the transfer mode from one-drop-per-pulse to an undesired irregular pattern. Besides, a quantitative analysis of the heat fluxes into the electrode is further conducted, and the result shows that power source dynamics only has a quite slight influence on the heat transfer behavior. (C) 2018 Elsevier Ltd. All rights reserved.