This paper proposes generalized topology and design method for the new wideband phase shifters based on multimode resonator (MMR). Based on this topology, the proposed phase shifters under operation of different resonant modes can be designed. Meanwhile, the phase properties and respective operation bandwidth, including return loss and phase shift bandwidths, are both analyzed. The results have clearly shown these introduced multiple modes can dramatically enhance operation bandwidth. Thus, the proposed phase shifters based on MMR can obtain wider bandwidth than traditional wideband phase shifters while maintaining simple design process and geometry. The design method has been well verified by testing a fabricated prototype of 90° phase shifter.