Abstract：Astrophysical observations ranging from dwarf galaxies to galaxy clusters indicate that dark matter halos are much more diverse than predicted in the prevailing cold dark matter theory. In this talk, I will show that self-interacting dark matter can provide a unified solution to a number of long-standing puzzles in astronomy and astrophysics, including the diverse galaxy rotation curves, radial acceleration relation, dark matter distributions in Mike-Way satellite galaxies and density cores in galaxy clusters.