An effective method for for controlling the absorption frequency of terahertz (THz) absorber based on graphene is presented in this paper. The absorber consists of graphene-dielectric stack with a resistive sheet on top layer and a perfect electric conductor placed at the bottom layer. A circuit model for graphene absorber was introduced to analyze the mechanism of the absorber. By changing the surface conductivity of graphene, fine tuning of the absorption resonances is achieved. The result of the proposed circuit model can be individually validated with the full-wave simulations, which are in a good agreement. In addition, the double-layer graphene-dielectric stack absorber exhibits stable resonances with respect to the incident plane wave at all oblique angles.