Finite element analysis software ANSYS is used to simulate the temperature distribution of 2A12 irradiated by continuous wave (CW) laser and long pulsed laser. The effect of different intervals of time between the two beams on the maximum temperature of the center and the size of molten pool and the effect of different combinations of the two lasers′ radiuses are investigated. The results show that the maximum temperature of the center increases by increasing the interval of time. The temperature rise induced by long pulsed laser increases when the interval of time is larger than one specific value. The maximum temperature of the center and the size of molten pool are mainly decided by the long pulsed laser which has a relatively higher peak power, the continuous wave laser used to preheat the material can significantly increase the size of molten pool when its power density is at 105 W/cm2 level.