A new path planning method is proposed for the electronic warfare UAVs to find the optimum interference path. The model of a UAV's interference to radar early warning is established. Then, according to the angular velocities of the UAV and the aircraft for penetration relative to the early warning radar and other constraints, the optimum path for a single UAV is obtained. The simulation results show that: the method makes full use of the UAV's speed for covering the aircraft penetration, and can save UAV resources greatly.