We systematically investigate the alpha-decay half-lives of three kinds of exotic nuclei in the framework of the density-dependent cluster model.This includes: (1)alpha-emitters approaching the N=Z line; (2) the neutron-deficient Pb and Po isotopes;(3) the exotic N=125, 126, and 127 alpha-emitters.The theoretical results are analyzed and discussed in detail.Good agreement between experiment and theory is obtained by taking nuclear structure effects into account.