The　optical　transmission　characteristics　for　the　hollow　carbon-coated　Fe3O4　colloidal　photonic　crystal　have　been　calculated　with　the　finite-difference　time-domain　(FDTD)　method.　We　analyze　the　influence　of　the　factors　on　the　photonic　band　gap　(PBG)　that　include　lattice　constant　a,　the　number　of　the　particles　in　propagating　direction　N-y,　the　thickness　of　carbon　layer　H-c　and　Fe3O4　cluster　layer　H-f,　and　the　thickness　ratio　of　the　two　layers.　The　results　show　that　the　PBGs　red　shift　and　the　bandwidth　first　increases　and　then　decreases　with　the　increasing　a.　In　the　situation　of　increasing　N-y,　the　PBG　changes　from　irregular　to　uniform,　followed　by　the　oscillations　on　both　sides　of　the　PBG　growing　in　number　and　the　deepened　PBG　in　the　low-frequency　region.　The　PBGs　move　toward　the　low　frequency　direction　with　the　increase　of　H-c,　and　the　optimal　value　of　H-c　for　the　uniform　color　response　is　10　nm　similar　to　25　nm.　The　PBGs　red　shift　with　the　increasing　H-f,　and　the　first　bandwidth　increases　while　the　second　decreases.　The　optimal　H-f　for　the　ideal　PBG　is　35　nm　similar　to　55　nm.　The　stop　bands　move　to　the　high-frequency　direction　with　the　increasing　thickness　ratio　(H-c　:　H-f),　and　the　best　ratio　is　10　nm　:　55　nm　for　the　complete　PBG　and　wider　bandwidth.