Atomic　composite-structure　materials　play　an　important　role　in　energy　generation　and　storage　application　fields　for　their　advanced　performance.　Constructing　heterostructured　semiconductors　is　a　promising　strategy　to　devise　photocatalytic　systems　with　high　activity.　However,　most　studied　hererostructures　are　those　semiconductors　with　different　materials　formed　by　multi-steps,　researches　on　in-situ　formed　hererostructure　originated　from　the　same　precursor　are　few　reported,　and　the　effects　of　different　structure　ratios　on　photocatalytic　performance　are　ambiguous.　Here,　according　to　in-situ　temperature　X-ray　diffraction　and　transmission　electron　microscope　techniques,　a　nano-sized　in-situ　formed　heterostructure　of　TiO2　semiconductors　with　anatase　and　TiO2-B　crystalline　structures　were　designed,　their　structure　ratios　were　adjusted,　the　heterostructure　interface　and　photocatalytic　reaction　mechanism　were　also　detected.　Results　show　that　high-quality　heterojunction　and　optimum　structure　ratios　have　vital　influence　on　photocatalytic　performance,　there　is　an　obvious　synergetic　effect　between　anatase　and　TiO2-B　structure,　degradation　reactions　on　methyl　orange　(MO)　under　ultraviolet　light　irradiation　prove　that　the　highest　activity　toward　MO　removal　can　be　obtained　for　material　with　82.5%　anatase　structure.　(C)　2018　Science　China　Press.　Published　by　Elsevier　B.V.　and　Science　China　Press.　All　rights　reserved.