A metamaterial (MM) absorber is very attractive in the terahertz (THz) regime for its potential applications as a bolometer and thermal emitter. In this letter, we propose a transmission line model for the MM absorber in order to identify the basic absorption mechanism involved. Some strategies are put forward to widen the absorption bands to over 250 GHz. A new kind of MM absorber is designed, fabricated, and measured. The results show that a strong absorption of over 90% with a bandwidth of over 300 GHz is obtained, facilitating wide-frequency applications.