Annular　pool　fires,　frequently　happened　in　chemical　industries,　have　a　significant　influence　on　environmental　pollution.　Air　pollution,　greenhouse　gas　emissions,　water　pollution,　and　soil　contamination　are　general　ways　of　environmental　hazards　caused　by　the　annular　pool　fires.　This　study　built　upon　our　previous　study　(Environ.　Sci.　Pollut.　Res.,　2023,　30(21):　59781-59792.),　and　extended　to　investigate　the　combustion　and　fire　plume　flow　behaviors　of　annular　pool　fires,　both　with　and　without　air　entrainment　through　the　hollow　center　of　the　annular　pool.　Results　show　that　when　there　is　no　air　entrainment　through　the　hollow　center,　the　low　combustion　intensity　area　at　the　plume＇s　central　axis　gradually　extends　while　the　high　combustion　intensity　area　concentrates　at　higher　places　and　the　flame　height　increased　by　nearly　40%　from　a　solid　pool　(Din/Dout　=　0)　to　the　annular　pool　(Din/Dout　=　0.80).　Additionally,　the　area　with　high　combustion　intensity　is　more　concentrated　at　a　higher　position.　The　combustion　of　annular　pool　fires　was　found　to　be　dominated　by　non-premixed　diffusion　combustion.　The　center　of　the　annular　pool　fires　is　dominated　by　air　prior　to　flame　merging　and　by　fuel　vapor　after　the　merging　occurs.　For　annular　pool　fires　with　air　entrainment　through　the　center　of　the　pool,　the　combustion　intensity　increases　as　Din/Dout　at　the　plume　base　increases.　And,　the　flame　height　decreased　by　nearly　25%　as　Din/Dout　increases.　Flame　burning　occurs　both　on　the　outside　and　inside　of　the　plume,　exhibiting　a　＂double　layer＂　combustion　characteristic.　It　reveals　that　the　combustion　of　the　fire　plume　transitions　to　premixed　diffusion　combustion.　The　center　of　the　annular　pool　fire　is　predominantly　composed　of　air.　Understanding　and　controlling　annular　pool　fires　can　lead　to　new　methods　for　remediating　fuel　spills,　reducing　pollution　from　combustion,　and　advancing　research　in　fluid　mechanics.