Abstract: Estimation (SE) techniques play important rule to anticipate security possibilities and operation control. Optimizing SE gives a better quicker update on the state operation of the power system without nature of system modelling. In this study, distrusted power system state estimation based on firefly was proposed. Various scenarios including normal operation where centralized and decentralized power area introduced. The IEEE 13 bus systems tested and the results are compared with those obtained Weighted Lease Square (WLS) to demonstrate the validity of the proposed approach.