Belonging to the technical field of biomedical polymer materials, the invention discloses a beta-cyclodextrin based amphiphilic pH responsive star polymer and a preparation method thereof, a micelle system based thereon, a composite material and application thereof. The polymer has a structure shown as the formula (1) in the specification, wherein x=3-20, y=2-30, z=5-35, and n=2-10. The polymer can be reduced in situ to obtain nanogold with small particle size and good stability. The invention also provides a micelle system based on the polymer, the micelle system has strengthened entrapment ability to water-insoluble drugs, can efficiently load hydrophobic drugs, gold nanoparticles and other substances, realizes the combination of tumor imaging diagnosis and tumor chemotherapy, and improves the therapeutic efficiency of cancer. And the polymer is easy to control the proportion of each block, and can be applied to preparation of the water-insoluble drug loaded micelle system to satisfy the release requirements of different drugs.