The disclosure relates to a two-dimensional (2D) bismuth nanocomposite, and a preparation method and use thereof, and belongs to the field of nanobiotechnology. The 2D bismuth nanocomposite of the disclosure is an ultra-thin bismuth nanosheet that is loaded with platinum nanoparticles and modified with indocyanine green (ICG) and surface targeting polypeptide Ang-2. The 2D bismuth nanocomposite Bi@Pt/ICG-Ang2 of the disclosure can not only realize the targeted photothermal and photodynamic combination therapy for tumors, but also realize the dual-mode imaging combining CT and fluorescence imaging.