A novel photo-thermal model of selective photothermolysis (SP) was proposed by using an element-based 3D Monte Carlo method to simulate the laser transport in the tissue,a 3D Pennes bio-heat transfer equation with variable thermal properties and dynamic changing vaporization temperature to calculate the temperature distribution,and the Arrhenius equation to predict the thermal damage. It was shown that the numerical results are significantly affected by the trapped vaporization coefficient k. The results obtained with k=0,0.022,0.18 and 1 of this model are close to those obtained with constant 100 ℃,110 ℃ and 130 ℃ vaporization temperature and without vaporization of the SP model,respectively.