Abstract: In order to design the radiation-hardened oscillator of the DC-DC converter, in which the radiation-hardened performance of the SR latch is very important, a novel radiation-hardened SR latch is presented in this paper. The proposed radiation-hardened SR latch is based on space redundancy and has been designed and verified in a standard commercial 2P5M 0.25 μm process. The die area of the latch is 130 μm×50 μm. Total ionizing dose tolerance is 100kRad(Si) and single event effect immuning to LET is 85MeV-cm²/mg. Compared with the triple modular redundancy SR latch, the proposed radiation-hardened SR latch has less transistors, larger critical charge of the circuit node and higher success rate of the circuit immuning to single event upset when more than one circuit nodes are upset at the same time.