The enhancement effect of radiation heat transfer based on the multibands feature of radiative gas is analysed theoretically for the system of laminar-channel flow of high temperature C02 gas between two parallel heat absorbing surfaces. An integro-differential equation of energy conservation, which takes into account the multi-bands feature of the radiative gas is solved numerically, and the enhancement effect of heat transfer by installing a solid plate in radiative gas is calculated. From these calculations, it is shown that the enhancement of local heat flux by as much as 80% is obtained and that this enhancement effect is caused by the very high radiative heat flux from the solid surface to the heat absorbing surface, notwithstanding the slight decrease in the radiative heat flux from the gas by installing a solid plate. It is also made clear that the analysis using the conventional gray gas assumption overestimates the decrease in the radiative heat flux from the gas, and thus estimates a too small enhancement effect.