A high voltage with a very short duration and fast rising time is beneficial to generate uniform and diffuse plasma in dielectric barrier discharge (DBD) loads, and a power supply with a high power factor (PF) can reduce the impact on the power grid. According to two requirements, a unipolar high voltage pulsed power supply with power factor correction (PFC) is proposed in this paper. The power supply consists of a unipolar pulse high voltage generating unit, a PFC unit, and a driving circuit. By introducing a feedback clamping diode and a reverse current blocking diode in a flyback converter, repetitive nanosecond pulses are generated in the unipolar pulse high voltage generating unit. Because a discontinuous current mode strategy is adopted in the PFC unit and the driving signal is shared by the two units, a compact structure of the power supply is achieved, and a high PF is obtained. To validate the proposed pulsed power supply, an experimental setup is built for a DBD excimer lamp. The results show that the proposed power supply has the capability of not only providing a unipolar nanosecond pulse high voltage for the DBD excimer lamp but also achieving PF close to 1 and total harmonic distortion of less than 24%.