A　simple　and　effective　route　has　been　developed　to　synthesize　a　three-dimensional　(3D)　Mn3O4　hierarchical　architecture,　which　shows　a　flower-like　morphology　and　is　composed　of　Mn3O4　nanosheets.　Two　experimental　parameters,　hydrothermal　temperature　and　NaOH　addition　speed,　were　revealed　to　have　critical　effects　on　the　formation　of　the　morphology.　Furthermore,　these　Mn3O4　materials　were　successfully　applied　to　degrade　the　organic　pollutants　in　water.　Compared　with　Mn3O4　nanoparticles　and　nanorods,　3D　flower-like　Mn3O4　nanostructures　are　found　to　most　heavily　enhance　the　MB　degradation　efficiency　of　the　UV/H2O2　advanced　oxidation　process　(AOP),　which　comes　from　their　high　BET　surface　area　and　good　absorption　ability.