This paper presents an improved optimal power flow algorithm, which solves an optimization problem with equality constraints with converted inequality constraints. The standard OPF and the penalty function method should do reconstructing active constraints among the inequality constraints so that the activation of the inequality constraints has been imposing an additional burden to solve OPF problem efficiently. However the proposed algorithm converts active inequality constraints into the equality constraints in order to preclude us from reconstructing the procedures. The effectiveness of the new OPF algorithm is validated by applying the IEEE 14 bus system.