Abstract: Bidirectional DC-DC convertors with three-ports are the connector between the energy storing devices and load of DC-DC convertors. It is one of the key equipment to influence the load capacity of DC-DC convertors.Now the topological structures for bidirectional DC-DC convertors with three-ports have been widely investigated.However, modeling and control methods for bidirectional DC-DC convertors with three-ports cannot meet the high control performance. In order to solve the problem,multi-modality switch modeling and state feedback control approaches were presented by using switch theories and spectral norm stability analysis methods in this paper.Asymptotic stability conditions were derived by applying spectral norm methodology. Controller gains can be obtained by solving a set of linear matrix inequalities. Simulation results show that the given approaches have some advantages, such as short transient times, small steady state errors and switch without traces and so on, which can provide a new idea for studying DC-DC convertors.