In the present study numerical simulation of synthetic jet is performed to optimize geometric parameters and excitation frequency to maximize mass flow rate and velocity of the jet and to avoid separation on the airfoil. Geometric parameters include: diameter and height of the cavity and orifice and excitation frequency of diaphragm which are selected as variable parameters for optimization. Using Response Surface Method (RSM) in this research, the simulations for optimization of the momentum of jet flow are designed. After studies and initial simulations, the range of variations in the effective variable parameters for the maximization of the target function (jet velocity and mass flow rate) are determined. Then, using the RSM, 32 separate tests are defined based on geometric and frequency parameters to find a second-order relationship, which relates the target functions to their variable parameters and their interactions. In this case the RSM prediction for the maximum velocity and mass flow rate of the jet are 22.16 m/s 0.0006 kg/s, respectively. Using RSM to optimize the geometric parameters and excitation frequency, jet momentum increases considerably in comparison with the first simulation. The velocity, mass flow rate, and momentum of the jet are increased by 31%, 36% and 78%, respectively.