Dwell scheduling is an important module of phased array radars. In order to implement effective dwell scheduling, a scheduling method based on new synthetic priority is proposed, in which the scheduling model is founded from the viewpoint of scheduling gain. The scheduling gain integrates the synthetic priority of the task and the validity of scheduling this task, where the synthetic priority integrates the importance, urgency of the task and threat level of the target. Simulation results demonstrate that compared with the conventional dwell scheduling method, the proposed method improves the scheduling performance of phased array radars.