Bismuth　oxyhalides　have　attracted　more　and　more　attention　as　promising　photocatalysts.　Oxygen　vacancies　on　the　surface　of　BiOBr　play　an　important　role　in　enhancing　photocatalytic　activity.　In　this　paper,　we　present　a　facile　method　to　prepare　hierarchical　BiOBr　microflowers　with　surface　oxygen　vacancies　by　the　solvothermal　synthesis　route　in　the　presence　of　urea.　The　content　of　oxygen　vacancies　on　the　surface　of　hierarchical　BiOBr　microflowers　can　be　tuned　by　the　amount　of　urea　used　in　the　synthesis　process.　Moreover,　it　was　found　that　hierarchical　BiOBr　microflowers　with　oxygen　vacancies　exhibited　much　better　photocatalytic　activity　for　photocatalytic　degradation　of　Rhodamine　B　than　the　BiOBr　without　oxygen　vacancies.　Furthermore,　experimental　results　revealed　that　oxygen　vacancies　can　promote　effective　separation　and　transport　of　photo-generated　charges,　which　is　beneficial　for　photocatalytic　performance　of　BiOBr.　This　study　establishes　an　in-depth　understanding　of　defective　oxygen　vacancies　structures　in　Bismuth　oxyhalides　based　photocatalysts.　©　2018　Elsevier　B.V.