Design and construction of Z-scheme photocatalyst has been attracted much attention, which is a great challenge to develop highly efficient photocatalyst without the external redox mediators. Herein, a novel efficient redoxmediator-free Z-scheme BiPO4/BiOCl0.9I0.1 heterojunction is synthesized in situ via a mild 90 degrees C water bath reaction. The as-synthesized BiPO4/BiOCl0.9I0.1 heterostructure exhibits outstanding photocatalytic performance for degradation of phenol and Rhodamine B, approximately 2.6 and 4.3 times higher than that of BiPO4/BiOCl0.9I0.1, respectively. The BiPO4/BiOCl0.9I0.1 heterostructure have multiple vacancies and valence, such as Bi5+, Bi3+, Bi(3-x)+, I-, I-3(-), and IO3-, which could facilitate the charge separation and transfer in the photocatalytic process. The higher photocatalytic activity of redox-mediator-free Z-scheme BiPO4/BiOCl0.9I0.1 heterostructure could be attributed to the strong redox ability, multiple charge transfer channels via the various defects, and tight contact due to in situ synthesis. The finding provides some new insights for the design of effective direct Z-scheme photocatalyst with multiple defects.