The bismuth vanadate (BiVO₄) photocatalyst was successfully synthesized by an organic-aqueous hetero-phase reaction method using organic additives (oleic acid, oleyl alcohol, and oleylamine) to investigate the reaction mechanism. The BiVO₄ with a star-like morphology could be synthesized with oleylamine. Bismuth precursors formed by the interaction between bismuth and the amino group of oleylamine were nano-sized complex particles with amorphous phase, finally resulted in the formation of star-like morphology. Moreover, BiVO₄ synthesized with oleylamine showed excellent photocatalytic activity on degradation of rhodamine B.