Gallium borates semiconductors have been developed as effective photocatalysts for water splitting driven by UV light irradiation, but there is no relevant study for the CO₂ photoreduction application. Herein, we report the first systematic investigation of open-framework gallium borate—Ga₉B₁₈O₃₃(OH)₁₅•H₃B₃O₆•H₃BO₃ (Ga-PKU-1) applying to photocatalytic CO₂ reduction under visible light irradiation by doping Fe³⁺ ion doping onto the framework. Using hydrothermal method, a series of Fe³⁺-incorporated Ga-PKU-1 have been successfully obtained, and a high Fe³⁺-to-Ga³⁺ substitution content (~10 atom %) can be achieved. The Ga-PKU-1:xFe³⁺ (x = 0.02 ~ 0.10) photocatalysts are characterized completely by diverse tests (e.g., XRD, XPS, UV-Vis DRS, SEM, N₂ sorption). The effective replacement of Ga³⁺ ion by Fe³⁺ ion could inhibit the degree of crystallinity of Ga-PKU-1, and also significantly expands the scope of spectral response from UV light to visible light. Compared with bare Ga-PKU-1, Ga-PKU-1:0.10Fe³⁺ exhibits remarkable CO formation rate of 3.2 μmol/h/g at 30 °C, and the selectivity for CO evolution exceeds 91.4 %. Besides, the CO formation rate increases to 8.3 μmol/h/g after thes loading of Ag as the co-catalyst. After four cycles of photocatalytic CO₂ reduction reaction experiments, it still gives constant CO evolution rate and the catalyst is stable. Furthermore, the thermal behavior research indicates Ga-PKU-1:xFe³⁺ could maintain structural stability at 400 °C.