This paper presents a novel triple-band power divider, which is constructed with two M-shaped triple-frequency impedance inverters. Each M-shaped inverter contains a section of transmission line, which is loaded with one stub at each end and a triple-frequency impedance block at the center point, exhibiting in an M-shape. The parameters of the inverters can be deduced with the even- and odd-mode analysis of the circuit. For validating the design theory, a triple-band power divider working at 1.5GHz/2.7GHz/3.5GHz is designed and fabricated. The measured results agree well with the simulation, demonstrating the feasibility of the circuit. This triple-band power divider features in compact dimension and fully-controllable three working frequencies.