The h-LuFeO₃ is a kind of narrow band gap hexagonal ferrite material, with a good application prospect in the field of ferroelectric photovoltaic. However, the low polarization intensity of h-LuFeO₃ makes the recombination rate of photogenerated electrons and holes large, which is not conducive to the improvement of the efficiency of h-LuFeO₃-based ferroelectric photovoltaic cells. In order to improve the ferroelectricity and optical absorption properties of h-LuFeO₃, the first principles method is used to calculate the doping formation energy values of In atom at different positions of h-LuFeO₃, and the most stable doping position is determined. The comparisons of band gap, optical absorption performance and polarization intensity among h-Lu_1-xIn_xFeO₃ (x = 0, 0.167, 0.333, 0.667) are made. With the increase of In doping, the cells of h-Lu_1–xIn_xFeO₃ stretch along the c-axis. The ratio of the lattice constant c/a increases from 1.94 at x = 0 to 2.04 at x = 0.667 when all the positions of In replace P1 position. Using the qualitative calculation of Berne effective charge, the results show that the ferroelectric polarization intensity of h-LuFeO₃, h-Lu_0.833In_0.167FeO₃, h-Lu_0.667In_0.333FeO₃ and h-Lu_0.333In_0.667FeO₃ along the c-axis are 3.93, 5.91, 7.92, and 11.02 μC·cm^–2, respectively. Therefore, with the increase of the number of In atoms replacing Lu atoms, the lattice constant c/a ratio of h-Lu_1–xIn_xFeO₃ increases, which can improve the ferroelectric polarization strength of the material. By analyzing the density of states of h-LuFeO₃ and h-Lu_0.333In_0.667FeO₃, we can see that In doping enhances the Fe-O orbital hybridization in h-Lu_0.333In_0.667FeO₃, and makes the optical absorption coefficient of h-Lu_0.333In_0.667FeO₃ in the solar light range larger. In summary, In doped h-LuFeO₃ is an effective method to improve its polarization intensity and optical absorption coefficient, which is of great significance for improving the performance of ferroelectric photovoltaic.