By combining a time-driven mechanism with a state-driven mechanism, a new switching strategy is designed to stabilize the switched linear systems with two unstable subsystems. Under this strategy, the Lyapunov-like function of the system is not necessary to be decreasing in both time-driven and state-driven mechanisms, which permits the subsystems to have a longer dwell-time to reduce the switching frequency remarkably. For suitable assumptions on the system dynamics, the system with time-varying disturbances has a good robust stability under the designed switching strategy. Moreover, when the system is observable, an observer-based combined switching law is designed, which robustly stabilizes the perturbed systems.