Construction of p-n heterojunction is an effective strategy to obstacle the rapid recombination of photo-generated carriers for single photocatalyst. Herein, visible-light-active Bi 2 O 3 /Bi 2 O 4 p-n junction was prepared by a one-pot hydrothermal method, using Bi(NO 3 ) 3 ·5H 2 O, KCl, and NaBiO 3 ·2H 2 O as precursors. The in-situ formed BiOCl reacts with NaBiO 3 ·2H 2 O during the hydrothermal process, producing the target product of Bi 2 O 3 /Bi 2 O 4 p-n heterojunction. As expected, the obtained Bi 2 O 3 /Bi 2 O 4 heterojunction photocatalysts exhibited higher photocatalytic activity than Bi 2 O 4 for the degradation of MO (methyl orange) and phenol under visible-light irradiation. The superior photocatalytic performance of Bi 2 O 3 /Bi 2 O 4 hybrid is mainly attributed to the improved separation efficiency of e - -h + pair induced by the internal electric field of p-n junction. The present work may provide a rational and facile strategy to construct a highly efficient Bi 2 O 4 -based p-n heterojunction photocatalyst toward pollutant removal.