In this study our aim is analysis of heat transfer in an internal combustion engine. In an internal combustion engine combustion chamber all three modes of heat transfer (conduction, convection and radiation) are important and effective. - Convection and conduction problems are not as complicated as radiation problem because gases in cylinder make a participating media .in this study a solver is developed in a software which can solve combustion, heat transfer and turbulence problem simultaneously. In order to verify the solver, experimental data of a furnace is used, using the experimental data and the model the problem is solved and verified. Finally in order to study the effect of radiative heat transfer in an internal combustion engine cylinder, the simplest case is considered that is injecting a fuel jet in a simple cylinder. The model can predict thermal critical points in which pollutant form and knock phenomenon begins. Results also shows radiation heat transfer may change Temperature up to 50 percent especially in media which contains higher density of water vapor, carbon dioxide and soot.