In this paper, a novel SEU/SET hardened PFD is proposed in order to reduce the SEE sensitivity of traditional D flip-flop type PFD. SPICE simulation shows that this structure has very high accuracy. Compared with traditional PFD, the electrical properties of PLL with radiation harden PFD are not changed. Compared with the number of hit nodes which can cause PLL jitter both for D flip-flop type PFD and radiation harden PFD, the number of sensitive nodes is reduced by 80%, indicating that the anti-radiation of the proposed PFD is quite effective.