Compared to the traditional method of fission energy local deposition, incorporating photon transport and photon heat release results in a slightly different neutron flux due to power normalization, which furthering impacts the burnup calculation. To asses this effect, this paper develops a coupled neutron–photon transport and burnup calculation model based on the deterministic two-step method. The lead–bismuth fast reactor benchmark RBEC-M was used to analyze the effects on physical quantities such as nuclide density, eigenvalues, and power distribution. The result shows that the photon effect lead to the production of more fissile nuclides, a slight increase in the rate of eigenvalue change, a significant improvement in the precision of heat release calculations in the breeding zone, and a minor flattening effect on the power distribution in the fuel assembly. Therefore, considering the impact of photon transport and photon heat release can enhance the accuracy of physical quantities of the fast breeder reactors.