Abstract: A method for energy optimization based on the partitioning, assignment, and task mapping of voltage-frequency islands is proposed, considering the issue of energy optimization of Network-on-Chip (NoC) that supports voltage-frequency islands. The energy consumption of the processor is reduced by the partitioning of voltage-frequency islands under processor reliability constraints; the number of complex routers between different voltage-frequency islands is decreased by the voltage-frequency islands assignment strategy of near convex region selection; and the energy consumption of system communications is reduced through NoC mapping optimizations by quantum-behaved particle swarm algorithm. Experimental results show that the presented algorithm can significantly reduce the NoC system energy consumption with the requirements of NoC processor reliability satisfied.