The invention relates to a preparation method and application of titanium dioxide carbon nanometer composite material-polymer composite hydrogel, and relates to a medicine for effectively solving the problems in tumor treatment and application thereof in a heat sensitizing agent, a photosensitizer and an initiating agent in antineoplastic thermotherapy and photodynamic therapy. The method comprises the followings: carrying out in-situ growth of titanium dioxide molecules on the surface of a carbon nano tube by using a hydrothermal method, and generating oxygen radical under a lighting effect to trigger a photosensitive monomer decorated by polyethyleneglycol to form hydrogel with the particle diameter of 1 nm to 1000 nm, wherein the mass ratio of a carbon nano tube and titanium dioxide is 1: (1-20), the titanium dioxide is of anatase titanium dioxide or rutile titanium dioxide, the hydrogel provided by the invention can effectively prevent loss of the photosensitizer and the heat sensitizing agent, reduce harms to normal cells around, improve the effective concentration of tumor tissue in a titanium dioxide carbon nanometer composite material, achieve the purpose of one time dosing for multiple treatments to a tumour part and enhance the antineoplastic curative effect, and can be used for wrapping a photosensitive medicine with antineoplastic activity, chemotherapy drugs or gene therapeutic agents.