An improved “mass–spring” model to analyze the entire short-circuiting transfer (SCT) dynamic process based on the association between the arcing and circuiting phases has been proposed. This paper analyses the basic characteristics of displacement of the droplet mass center and oscillation velocity of droplet variation. In addition, the effect of welding current on the short-circuiting frequency is studied. The results of the simulations conducted agree well with the experimental results obtained. An analysis method for optimal welding current during SCT is also proposed, and the droplet transport stability is discussed. Simulation results demonstrate that the relative displacement of the droplet mass center and the average equivalent diameter of the transfer droplets are at a minimum under the optimal welding current condition. This research provides a reference for further simulation of the SCT process and useful guidance for the selection of optimum technics parameters.