Bismuth vanadate as photoanode with suitable bandgap and appropriate valence band positions is generally very stable in aqueous solution and cheap, but the photochemical activity is usually limited by poor electron mobility and low oxygen evolution kinetics. Herein, we exhibit that the above-mentioned problems can be solved by introducing a foreign dopant (Mo6+) into the BiVO4 film to create a distributed n(+)-n heterojunction and combining the BiVO4 photoanode with cobalt-phosphate water oxidation catalyst to improve the oxygen evolution kinetic. We systematically study the relationship between the higher photoelectrochemical performance and Mo-doping and cobalt-phosphate (CoPi) modification by XRD, Raman, SEM, TEM, LSV, EIS, I-t, and Mott-Schottky measurements, and the CoPi-Mo:BiVO4 heterojunction photoanode shows a current density of 3.27 times higher than that of pristine BiVO4 photoanode. Then, we concentrate our attention on a novel perspective for understanding the photoelectrochemical mechanism of interfacial charge transfer with the Mo-doping and CoPi modification on the BiVO4 photoanodes. This work provides new insights into the rational design of novel photoanodes from various improvement strategies with high photoelectrochemical performance and further utilization for environmental practical applications.