Photodynamic Therapy is regarded as the best treatment for port wine stains, which has the main adverse effect of various degrees of pain (mild to moderate) during the illumination. Though the cooling and cold water have been used to reduce such pain, there is still no scientific evidence for these relief. In this paper, a realistic skin model is built to simulate the distribution of light under treatment, which helps control the light dose and temperature, and improve the clinical results. Comparing with the general parallel skin model, a curving stratum basale layer is used in this paper, and various blood vessel configurations such as single and multiple vessels with horizontally and vertically oriented, curve vessels, various vessel diameter and various radius of curvature of stratum basale layer are simulated. The results shows a more realistic modeling for the thermal damage and help to relief the pain in the treatment.