Abstract: Due to the randomness in the CO₂ short-circuiting arc welding, the adaptive model of droplet considering the initial size, the initial temperature and the time of short-circuits between drop and melting pool is set up in the numerical model. Then the three-dimensional transient model of CO₂ short-circuiting transfer welding pool was set up. In model, the asymmetric Gauss heat source was adopted taken into account the asymmetric of welding arc's heat flux density along welding direction, the VOF model was adopted to track the gas-liquid interface, the enthalpy-porosity technique was used to compute the momentum sink in the mush zone; the additional source term method was used to add the main force of pool, such as arc pressure, the electromagnetic force, the buoyancy and so on. The evolution of the temperature field and flow field was computed with the model in the CO₂ short-circuiting arc welding of 6mm thick low carbon steel. The probability density distribution of short-circuiting time interval and the final weld formation under the simulation condition was well agreed with experimental result.