Photocatalytic reduction of carbon dioxide into valuable chemicals is a sustainable and promising technology that alleviates the greenhouse effect and energy crisis. In this study, the Mn₃O₄/FeNbO₄ type II heterojunction photocatalyst with a core-satellite structure was synthesized by the facile soft chemical method. The formation of a nano-heterojunction is supposed to effectively improve light capture, charge transfer, and interfacial charge separation in the photochemical reaction. Meanwhile, the heterojunction has a good ability to capture and activate CO₂. Our results show that the prepared Mn₃O₄/FeNbO₄ photocatalyst exhibit obvious enhanced catalytic properties in the photocatalytic CO₂ reduction reaction, where the CH₄ yielding rate is 1.96 and 9.81 times those of FeNbO₄ and Mn₃O₄, respectively. The transient photovoltage test (TPV) shows that the low frequency electrons are crucial to the effective transfer of photogenerated electrons and holes in the Mn₃O₄/FeNbO₄ nano heterojunctions. Analysis of in situ Fourier transform infrared spectroscopy (FTIR) verifies the effective CO₂ adsorption on the Mn₃O₄/FeNbO₄ surface and the high selectivity of CH₄ products. These properties of the Mn₃O₄/FeNbO₄ photocatalyst infer its broad prospects in the fields of carbon fixation and energy conservation.