Abstract: A method for reliability and energy optimization using voltage-frequency island (VFI) partitioning, assignment, and task mapping is proposed for a network on chip (NoC) which uses 2D-Torus topology and supports voltage-frequency islands. The method adopts a progressive optimization approach. A moving threshold function between different voltage-frequency islands is defined according to the dynamic processing energy of IP cores, energy overhead of VFIs, and reliability costs. The division and allocation of the voltage-frequency island is based on the moving threshold function. A ternary correlation quantum-behavior particle swarm optimization (PSO) algorithm is used for the IP core mapping, during which, the reliability cost is fully considered to increase the reliability of the NoC system. The experimental result shows that the reliability of the NoC system is increased without consuming too much energy, and the energy consumption of the whole NoC system can be reduced effectively.