: Comprehension of the phenomenon of heat transfer and related thermomechanics in soft tissues is of great importance. It contributes to description of high thermal radiation on biological bodies, specifically, thermomechanical damage to tissue and a variety of medical applications. Presence of blood and its thermal roles in living tissues such as blood perfusion, convection, perfusion of arterial-venous blood through capillaries and physiological processes, including metabolic heat generation and also heat conduction and interaction with environment, make this process complicated. One of the most difficult problems of heat transfer estimation in living system is the assessment of the effect of blood circulation. The vasculature geometry and mathematical description of convective heat transfer in tissues are very intricate problems. This study investigated the significance of blood vessels in living tissue which its surface is subjected to radiation by a novel approach to evaluate convective heat transfer between blood in vessels and the tissue across the vessel walls. The objective of this simulation is to reflect the structural reality of skin and blood vessels and to analyze the heat transfer. The governing equation is that of Pennes Bio-Heat Transfer Equation. Here, the convective heat exchange between pre-arteriole, post-venule vessels and the tissue across the vessel walls is considered. Furthermore, characteristics of blood which is considered to be a non-Newtonian fluid, is estimated based on Power Law model. In order to evaluate transient convective heat transfer between the tissue and vessels, temperature distributions in three-dimensional space are obtained by solving continuity, momentum and energy equations numerically. The pervious works apply a constant Nusselt number which is derived based on steady condition to evaluate heat transfer between vessels and tissue. In this paper, we consider the skin as a three-dimensional structure including three layers embedded with multi-level blood vessels, i.e. artery and vein. The countercurrent vessels, with circular cross section area, are considered to be optimally branched. The diameter ratio of the branches is determined based on extension of Murray's Law (Cube Law) as well as length-doubling rule is applied for determination of blood vessels lengths in different levels. Moreover, the angle of vessel branches is evaluated based on physiological principle of minimum work to the angle. Using temporal temperature field, the skin damage is represented as a chemical rate process based on Arrhenius equation. Simulation of skin burn injury by the novel approach to evaluate temperature distribution and convective heat transfer in living tissue has improved in this study. The present vessel network model is a realistic model that simulates many of the major features of the heat transfer in tissues and can of practical use. According to results Skin's blood vessels play a crucial role in regulating body temperature. In this study by solution of momentum and energy equations, we found that the Nusselt number in terminal branches is around of eight which is consistent with the magnitude that is derived based on analytical equations for non-Newtonian fluid using power law model. The temperature results show the low temperature contours along the artery and high temperature contours along the vein which indicate the blood in the artery acts as a heat sink and the blood in the vein is carrying heat out of upper parts of tissue. Due to the fast convection traort with blood flow in vessels and blood perfusion into tissue through terminal vessels wall and heat exchange in capillary bed blood has tremendous effects on the resulting heating temperature. Skin burn degrees based on this new approach are reported in this project. Key Words : numerical simulation, three-dimensional skin structure, branched vasculature, skin burn injury