This paper describes an approach to combine spintransfer torque Magnetic Tunnel Junction (MTJ) based non-volatile flip-flops (NVFFs) with power gating techniques to enable anytime power-off and instant power-on. We analyzed the NVFFs which are expected to realize nonvolatile power gating (NVPG) for a microprocessor. We evaluated the NVFFs by the area, the performance and the energy dissipation. We also investigated effectiveness of NVPG that combines the NVFFs with the 32-bit microprocessor core. The simulation results showed that the NVPG reduced more energy dissipation when the idle time of the microprocessor is longer than 5ms at 25°C as compared with the conventional SRAM-backup scheme. Additionally, the NVPG was able to reduce more energy dissipation at higher temperature.