Abstract: The out-of-plane equivalent thermal conductivity of honeycomb cores at high temperature was analysed using finite element method,the analysed results were compared with the test results and the results from semi-empirical formulat,he comparison shows that finite element mathod could be used to predict the out-of-plane equivalent thermal conductivity of honeycomb cores.The out-of-plane equivalent thermal conductivity of honeycomb cores at low temperature was also analysed using finite element method,and the radiation in the honeycomb cores has little effect on the out-of-plane equivalent thermal conductivity of honeycomb cores below 0℃,meanwhile an approximate formula to predict the out-of-plane equivalent thermal conductivity of aluminum alloy honeycomb cores below 0℃ is obtained.