A　bi-crystalline　(monocline　and　anatase)　titanium　dioxide/multi-walled　carbon　nanotubes　(TiO2/MWNTs)　composite　was　prepared　through　the　hydrothermal　reaction　of　tetrabutyl　titanate　and　sodium　hydroxide　with　butyl　end-capped　fatty　alcohol　ethoxylates　as　phase　regulator,　and　its　photocatalytic　property　under　visible　light　irradiation　was　investigated.　The　results　show:　the　adding　of　MWNTs　can　affect　crystalline　phase　and　improve　the　photocatalytic　activity　of　TiO2,　the　product　with　5%　MWNTs　exhibits　the　greatest　photocatalytic　degradation　rate;　the　photocatalytic　activity　of　the　products　greatly　increases　with　the　increase　of　calcination　temperature.　The　effect　of　doping　MWNTs　originates　from　(1)　facilitating　the　formation　of　bi-crystalline　phase　with　monocline　and　anatase,　and　(2)　excellent　conductivity　of　MWNTs,　or　(3)　the　carbon　doping　effect　rooting　in　the　breaking　down　of　MWNTs　under　higher　temperature.