To determine the high temperature thermal conductivity of small samples such as granular or powder materials which can not be measured by any existing method，the method to estimate their values from the thermal conductivity of the mixture of small samples and gases was proposed． From a result of investigating the relation between the thermal conductivity for the mixture （λm，measured by a transient hot wire method at high temperatures） of a granular solid with λs／gas withλf and an absolute temperature（T），the following experimental relation obtained by modifying
the Fricke’s equationλF was established．
λm＝λF＋4×10-4（T／100）3
For cases where the thermal conductivity of granuar materials is less than 3W・m-1K-1，the thermal conductivity of granular materials at high temperatures can be estimated by the relation．
