Bacterial colony chemotaxis（BCC） optimization algorithm is used in reactive power optimization problem in electric power system in this paper. The modeling of reactive power optimization is established taking the minimum network losses as the objective. Reference axes are three bacterial values: generator voltage， transformer tap and capacitor tank， respectively. All of bacterial values for every space position forms initial matrix in reactive power optimal modeling. Bacterium finds its foraging way with whole search ability by bacteria’s searching strategy rule. Convergence speed is improved by optimizing initial parameters. This method is applies to the IEEE 30， IEEE 57， IEEE 118 system and compared with IMGA and CPSO optimal method， the result is acceptable.