In injection molding, the injection pressure is often limited by the capacity of injection machines. Therefore, for large-volume part, multiple gates are needed so that the maximum flow path can be shortened, with a corresponding decrease in injection pressure. Many components produced by injection molding today require more than one gate. As multiple gates affect resin flow in a mold interactively, their locations might not be easily determined. For a mold with two gates, a pressure gradient search scheme (PGSS) is proposed to optimize their locations in this investigation. A search direction associated with pressure gradient is developed based on the physical nature of the mold-filling process. An alternative scheme based on genetic algorithm is also employed for comparison. Through minimizing the objective function of injection pressure, the optimum gates can be located to achieve balanced flow. Examples indicate that the proposed pressure gradient search scheme is more efficient than genetic algorithm for two gate location optimization.