Core/shell structured C3N4/BiPO4 photocatalyst is fabricated via a facile ultrasonic dispersion method. The thickness of the shell may be controlled by tuning the amount of C3N4 in the dispersion, which determines the enhanced level of photocatalytic activity. The optimum photocatalytic activity of C3N4/BiPO4 at a weight ratio of 4% (C3N4/BiPO4) under UV irradiation is almost 4.5 times as high as that of reference P25 (TiO2) and 2.5 times of BiPO4. More attractively, the dramatic visible light photocatalytic activity is generated due to the C3N4 loaded. The enhancement in performance is demonstrated to be the match of lattice and energy level between the C3N4 and BiPO4. This match facilitates the separation and transfer of photogenerated electron–hole pairs at the heterojunction interfaces and may be important for other core/shell structured materials. In addition, this method is expected to be extended for other C3N4 loaded materials.