Abstract: According to the characteristic of weaving welding, an arc swing ladder model was established on basis of strip heat source and numerical simulation of temperature field inQ345 steel plate butt joint with weaving welding was done using commercial software SYSWELD. The transient temperature field and thermal cycle curves in the welded zone were obtained. The results showed that the transient temperature field with arc-weaving ladder model was different from that with strip heat source model, and the weld pool with ladder model was elliptical with small head and big rump when the heat source moved from the middle to both sides. The thermal cycle curves with ladder model were also different from those with strip heat source model, and they had a wave crest both in heating and cooling, which reflected that the weld was affected by the arc weaving upon heating and cooling.