This paper proposes a sophisticate application of redox flow batteries (RFB) coordinate with Interline Power Flow Controller (IPFC) for the improvement of Load Frequency Control (LFC) of a multiple units two- area power system. The Interline Power Flow Controller is to stabilize the frequency oscillations of the inter-area mode in the interconnected power system by the dynamic control of tie-line power flow. The redox flow batteries, which are not aged to the frequent charging and discharging, have a quick response and outstanding function during overload conditions. In addition to leveling load, the battery is advantageous for secondary control in the power system and maintenance of power quality of distributes power resources. The Bacterial Foraging Optimization (BFO) algorithm is use to optimize the parameters of the cost functions for designing the integral controller. Compliance with North American Electric Reliability Council (NERC) standards for Load Frequency Control has also been establishes in this work. Simulation studies reveal that the RFB coordinate with IPFC units has greater potential for improving the system dynamic performance.