In order to enhance the measurement accuracy of spaceborne solar irradiance and make its traceability value closer to the world radiometric reference, a finite element method is used to correct the opto- electric nonequivalence of solar irradiance absolute radiometers (SIAR). The positive cone cavity is used in the SIAR and the heating wires are embedded into the thin walls. Thus, the opto-electric nonequivalence of SIAR is mainly derived from the drift driven by the first specular reflection. As it is difficult to measure the error in laboratory, the finite element system based on the structure of SIAR is established to quantitatively correct the nonequivalence, the relative error between the results obtained by the experiment and the finite element system is 0.86%. The results show that the power distribution of laser heating and electric heating is different due to the drift driven by the first specular reflection, the nonequivalence factor is 1.0000589, and the uncertainty is 3.4 × 10^{- 6}. The radiant power measurement is modified according to this factor, and the final total solar irradiance value is (1365.70 ± 1.24) W/m². The correction improves the revision system of SIAR.