This paper proposes an approach for optimal power flow (OPF) problem in order to improve the power system stability because Stability is one of the important constraints in a power system operation. Often trial and error heuristics methods are used to improve the stability of the power system, but that can be costly and imprecise. A new methodology that eliminates the need for repeated simulation to determine a transiently secure operating point is presented. The methodology involves a stability constrained Optimal Power Flow (OPF). Particle swarm optimization (PSO) algorithm is adopted to realize the OPF process. The method is programmed in MATLAB and implemented to a fourteen-bus test power system. The results show the ability of the proposed method to find optimal (or near optimal) operating points in different cases. This paper proposes this novel approach to solve OPF problem with improvement in the power system stability also.