In this work, we developed a simple method to fabricate BiVO4 photoanode consisted of mesoporous nano particles (meso-BVO) by using P123 as a pore maker. Owing to the unique mesoporous nanostructure, meso-BVO exhibits higher BET surface areas, shorter hole transit distance and higher electrical conductivity than does pristine BiVO4 photoanode (BVO) consisted of solid nanoparticles. As a result, the charge separation efficiency and PEC performances of meso-BVO have been greatly improved. Meso-BVO yields a photocurrent of 2.19 mA/cm(2) (1.23 V vs RHE) and IPCE of 39% (420 nm), which is 2.52 and 2 times as high as that of pristine BVO. With the assistance of Mo6+ ions doping and Co-Pi, the PEC performances could be further improved by addressing the inefficient electron transport and slow water oxidation kinetics. Co-Pi/Mo:meso-BVO yields a photocurrent of 4.57 mA/cm(2) (1.23 V vs RHE) and IPCE value of 65% (420 run). The enhanced PEC performance can be mainly ascribed to the perfect charge separation in the bulk of Co-Pi/Mo:meso-BVO photoanode. Our work provides a simple method to fabricate high efficient BiVO4 photoanodes consisted of mesoporous nanoparticles with enhanced bulk charge separation efficiencies.