Ag-TiO2　composite　nanotubes　were　synthesized　for　the　first　time　by　using　the　hydrothermal　crystallization　with　TiO2,　NaOH　and　AgNO3　at　700　°C　in　ambient　atmosphere.　The　synthesized　nanotubes　were　then　characterized　using　TEM　and　XRD　techniques.　The　experimental　conditions　for　the　nanotube　synthesis　and　the　photocatalytic　degradation　mechanism　of　methyl　orange　(　MO　)　with　nanotubes　as　a　photocatalyst　were　also　examined.　The　results　show　that　there　is　a　distinct　effect　on　nanotube＇s　photocatalytic　characteristics　under　different　synthesizing　conditions　such　as　melting　and　hydrothermal　crystallization　temperature　and　time.　The　photocatalytic　degradation　rate　(η)　reached　about　99　%　when　the　reaction　was　kept　for　4　h　and　the　initial　concentration　of　MO　solution　(C0)　was　4　mg/L.　The　relationship　between　the　rate　constant　(k)　of　the　degradation　and　C0　conformed　to　an　order　of　0.996　6　reaction.