It was previously claimed by the author that black holes can be considered as topological insulators.Both black holes and topological insulators have boundary modes,and the boundary modes can be described by an effect-ive BF theory.In this paper,the boundary modes on the horizons of black holes are analyzed using methods de-veloped for topological insulators.BTZ black holes are analyzed first,and the results are found to be compatible with previous works.The results are then generalized to Kerr black holes,for which new results are obtained:dimen-sionless right-and left-temperatures can be defined and have well behavior in both the Schwarzschild limit a → 0 and the extremal limit a → M.Upon the Kerr/CFT correspondence,a central charge c = 12Mr+can be associated with an arbitrary Kerr black hole.Moreover,the microstates of the Kerr black hole can be identified with the quantum states of this scalar field.From this identification,the number of microstates of the Kerr black hole can be counted,yielding the Bekenstein-Hawking area law for the entropy.