For basic Bacterial Colony Chemotaxis (Bacterial Colony Chemotaxis, BCC) the defects existing in the algorithm was improved, with weight coefficient was introduced to the basic BCC algorithm of bacteria change formula, the algorithm can fast convergence around several optimal solution and a detailed search, so as to find the global optimal solution; Introduces the dynamic adjustment mechanism of bacteria perception scope, improve the optimization precision of the algorithm; Introduced the book, the bacteria in the process of optimization, the optimal value of suspense in the book, so as to avoid the optimum abandoned by random. In this paper, based on optimal power flow (OPF) calculation model of the available transmission capacity (ATC), and with the improved BCC algorithm to solve the model. By IEEE - 30 node test system as an example for the simulation calculation, and the calculated results were compared with basic BCC algorithm, the results show that IBCC algorithm can get the optimal solution with faster speed, its performance is superior to the basic BCC algorithm.