Display omitted •A novel WO3@W18O49 branched homojunction was fabricated for the first time.•The WO3@W18O49 branched homojunction exhibit superior interfacial charge separation.•The enhanced interfacial charge separation was confirmed by series experiments.•A novel design strategy for full-spectrum responsive photocatalyst is proposed.•The degradation pathway of 2,4-DCP is proposed. Interfacial charge separation is a fundamental and crucial process in photoelectric conversion for composite photocatalyst. In this work, the interfacial charge separation performance was investigated on a nonmetallic branched homojunction, which is fabricated through solvothermal growth of W18O49 nanofiber (as branches) onto WO3 microrods (as backbones). The ultrafast transfer of photogenerated electrons from the WO3 backbones to the W18O49 branches across the contact interface was demonstrated by a series of experiments and characterizations. The contrast experiment showed that the WO3@W18O49 homojunction exhibited superior interfacial electron transfer capacity to the BiVO4@W18O49 heterojunction, the calculated interfacial charge separation efficiency of WO3@W18O49 was 51.3%, which was more than twice as that of BiVO4@W18O49 (24.2%). Upon localized surface plasmon resonance excitation by low-energy NIR photons, the full-spectrum light driven photo-degradation for 2,4-DCP was realized. The branched structure favors the enhancement of light scattering and absorbing. Meanwhile, the homojunction structure leads to a low impedance interface and increased electric conductivity. Thus, the WO3@W18O49 exhibited an enhanced photocatalytic performance under both full-spectrum and NIR light irradiation. This work provides a promising approach to design and fabricate novel photocatalysts with full-spectrum response ability and enhanced charge separation.