Abstract
It is observed through HST that the central surface brightness of early-type galaxies has an interesting diversity. Some have an obvious central flatten part, but the others do not. Thus, these galaxies could be classified into two types, i.e. core galaxies and power-law galaxies.In order to explain this diversity, we propose and construct dynamical models with supermassive binary black hole in given galactic halo potentials which could lead to the observational surface brightness, such as those described by Nuker law or Sersic law. In addition, the properties of equilibrium points and equal-potential surfaces in the systems will be investigated.