The invention discloses a molybdenum disulfide nanodot and polyaniline nanohybrid and a preparation method and application. The preparation method comprises the steps that 1, molybdenum disulfide nanodot powder is prepared; 2, an aqueous solution of aniline and an aqueous solution of sodium dodecyl sulfate are taken and mixed to be uniform, a mixed solvent is obtained, and the molybdenum disulfide nanodot powder and povidone are added into the mixed solvent to be stirred; 3, an ammonium persulfate solution is dropwise added into liquid obtained in the second step, stirring and centrifuging are conducted, green precipitate is obtained, freeze drying is conducted, and the molybdenum disulfide nanodot and polyaniline nanohybrid is obtained. The molybdenum disulfide nanodot and polyaniline nanohybrid has water solubility and biocompatibility, can encapsulate a large quantity of molybdenum disulfide nanodots, can be used for CT imaging, displays good and high near infrared absorption and good light and thermal stability and can be used for light and thermal treatment and infrared thermal imaging simultaneously. The preparation method is simple, the reaction condition is mild, the controllability is high, energy consumption is low, large scale is easy to achieve, and the cost is low.