本文通过数值模拟，计算出了Ｆｅ－Ｃ合金的共晶共生区，并以此作为实际加工中激光处理参数优化选择的手段．数学模型从计算物体表面温度场三维分布入手，考虑到激光空间 Ｇａｕｓｓ分布特性，得到物体表面温度梯度分布．结合枝晶分布ＫＧＴ模型以及共晶分布经修正的ＴＭＫ模型，得到一个完整的从激光重熔到共晶生长的计算模型，并计算了微观结构的共晶生长的范围． In this paper, the eutectic region of Fe-C alloy has been calculated by numerical simulation and used as a tool to optimize the laser processing parameters in practical processing. The mathematical model starts with the calculation of the three-dimensional distribution of the temperature field on the surface of the object. Considering the Gauss distribution in the laser space, the temperature gradient distribution on the surface of the object is obtained. Combined with KGT model of dendrite distribution and modified TMK model of eutectic distribution, a complete calculation model from laser remelting to eutectic growth was obtained, and the eutectic growth range of microstructure was calculated.