Photocatalysis, as an advanced oxidization process, has been extensively studied in environmental remediation. To suppress the recombination of photogenerated charge carriers, a novel oxygen-vacancy-rich black BiOBr/BiOBr isotype heterojunction has been successfully fabricated by surface hydrogenation. As-prepared samples were comprehensively characterized by various techniques. Photocatalytic activity of as-prepared samples was measured via degradation of colorless organic pollutant (phenol) in water under visible light. It was found that over 90% of phenol were removed over 210 min under visible light, which was double and 4.5 times higher than that of black BiOBr and pure BiOBr, respectively. The enhancement in photocatalytic activity may be attributed to the synergistic effects of isotype heterojunction and oxygen vacancy. Formation of heterojunction facilitated photogenerated charge carriers' separation. And the surface oxygen vacancies acted electrons acceptors and reactive sites in photocatalytic oxidization process. This work sheds a light on the significance of oxygen vacancies in improving photocatalytic activity.