A photo-excited tunable and broad band metamaterial absorber in the terahertz region is proposed. The metamaterial absorber is composed of three layers like the sandwich, the top layer is a ring metal-semiconductor square split ring and the bottom layer is a metallic ground plane, these two layers are separated by a dielectric spacer, which we choose as the polyimide. The conductivity of the silicon can be tuned actively with the incident pump power. We use the full wave simulation and the equivalent circuit parameter to analysis this absorber, and interpreted the phenomena showed when the conductivity of the silicon filled in the gap of ring is changed by the electric field. The proposed equivalent circuit parameter can save more time to design this kind of absorber in need. The proposed photo-excited tunable metamaterial absorber can also be used as terahertz modulators and switches.