In non-vacuum environments， radiation heat flux meters based on the electric substitution measurement principle face challenges such as intricate photoelectric inequality and hurdles in experimental testing and correction. To enhance the meter's accuracy， the photoelectric inequivalence source of the radiant heat flow meter was first analyzed. Subsequently， a thermal structure model for the radiant heat flow meter was developed by combining heat transfer theory with finite element analysis. The model's validity was then ascertained via a vacuum-to-air ratio experiment. Using this finite element thermal structure model， adjustments were made to address the inequivalence in the heat transfer process. The difference between the test results of vacuum-air responsiveness of the finite element model and experimental results is 1.7%， and the inequivalence of heat transfer is 0.28%. The photoelectric inequivalent correction coefficient is 1.002 35， and the relative uncertainty is 0.29%. Hence， this approach refines the radiant heat flux meter's correction system， improves its measurement accuracy， and furnishes valuable recommendations for further optimization and enhancement.