<p>The addition of S element can effectively make the melt pool show greater fluidity at low temperature, so as to achieve excellent cladding effect. The influence of S element on the solidification behavior of the cladding process is very complex, which occurs at the scale from macro to mesoscopic, thus causing the Marangoni flow state in the melt pool, affecting the flow of molten metal and the formation of the edge of the melt pool, and then affecting and changing the morphology of the cladding layer. It is significant to establish a macro-mesoscopic cross-scale model during laser cladding based on phase field method to quantitatively reveal the influence mechanism of S element. In this paper, a macro-mesoscopic cross-scale numerical model of ASTM 1045 laser cladding Fe60 process was established based on the phase field method. Firstly, the macroscopic influence mechanism of S element on the heat-flow coupling during cladding was discussed. Then, a numerical model of dendrite growth during cladding solidification was established to solve cladding phase field at mesoscopic scale. The mechanism of the influence of S element during laser cladding solidification at mesoscale was investigated. The results show that S element can change the direction of Marangoni convection in the melt pool, resulting in different growth trends of dendrites in different directions during solidification. S element can obviously reduce the solidification segregation phenomenon and increase the dendrite growth rate.</p>