To investigate the modification mechanism of mixed heterogeneous on photocatalysis, a series of Nd³⁺-doped BiVO₄ photo-catalysts with different Nd³⁺ contents were synthesized through a facile hydrothermal reaction. The samples exhibit Nd³⁺ content-dependent phase transition from monoclinic to tetragonal phase, as demonstrated by XRD and Raman analyses. SEM images show that the phase transition is accompanied by obvious morphology variation. Less than 1at% Nd³⁺-doped monocline BiVO₄ is composed of irregular particles, while more than 7at% Nd³⁺ doping results in tetragonal phase BiVO₄ of sphere-like or kernel with groove surface. When Nd³⁺content is in the range of 1at%-7at%, the micron cuboid bars appear in the samples. More importantly, monoclinic and tetragonal phase is concomitant in the product and a heterogeneous junction with staggered band structure is formed. The Rhodamine B degradation efficiencies of all Nd³⁺-doped samples are higher than those of undoped samples due to the regular morphology after doping. The formed heterogeneous junction inhibits photo-generated electrons and holes recombination of Nd³⁺-doped BiVO₄, inducing 99.4% catalytic efficiency in 4at% Nd³⁺-doped sample. The novel morphology and the intrinsic mechanism of photocatalysis enhancement upon Nd³⁺-doped BiVO₄ are obtained from the synthesis strategy and the energy band structure.