A thermal barrier coating(TBC) was applied to protect a turbine blade from high temperature combustion gas. The TBC consists of three different layers, which are a top coating, a bond coating, and a substrate. Because it has a low thermal conductivity and a relatively large thermal expansion ratio, the yttria stabilized zirconia(YSZ) is commonly used for a top coating. A bond coating and a substrate are metallic materials. One of main coating spallation cause is mis-match of thermal expansion coefficient between a top coating and a substrate. Many pores are made in a top coating when coating is deposited. It has an effect on thermal stress that occurs in the interface between a top coating and a bond coating. Therefore, in this paper, a research on the effect of pore on thermal stress was conducted by using finite element analysis.