Molecular　dynamics　simulations　have　been　conducted　to　study　the　interaction　between　anatase　TiO2(001),　(100),　and　(101)　surfaces　and　water　at　room　temperature.　The　dynamic　interfacial　structure　and　properties　of　water　on　anatase　TiO2　surfaces　are　obtained　by　analyzing　the　water　density,　the　diffusion　coefficient　of　water,　the　surface　charge　distribution,　electric　fields　and　the　electrostatic　potential　distribution.　The　simulation　results　have　revealed　that　a　highly-ordered　water　layer　structure　can　be　formed　near　to　the　anatase　TiO2　surface　and　have　also　given　the　Helmholtz　layer　width　and　potential　drop　at　the　water-TiO2　interface.　By　correlating　the　Helmholtz　layer　with　the　depletion　layer,　the　depletion　layer　widths　of　three　surfaces　(001)　,　(100),　and　(101)　have　been　calculated　as　474　angstrom,　237　angstrom　and　99　angstrom,　respectively.　The　resulting　order　of　the　photoelectrochemical　activity　of　the　anatase　TiO2　surfaces　is　(001)　＞　(100)　＞　(101),　which　is　consistent　with　the　experimental　results.　This　study　may　provide　a　useful　correlation　of　the　depletion　layer　with　the　Helmholtz　layer　based　on　simulations　results　for　the　prediction　of　the　behavior　and　the　control　of　photon-energy　conversion　devices.