A RRAM-based non-volatile flip-flop (NVFF) is designed to meet energy efficiency requirement for standby-power-critical applications in the deployment solution of IoT (Internet of Things). Adding only a pair of 1T1R cell into slave latch of a traditional FF can cut off the standby leakage at the cost of 4pJ write energy, and 20ps data retention time upon ideal power-on. The NVFF circuit is simulated and analyzed in HSPICE with a SPICE compact model of oxide-based RRAM on the conductive filament evolution model.