Abstract-In this paper, a new system is proposed for microstrip antenna (MSA) designing. Two main stages need for designing procedure. Firstly, modeling of rectangular MSA is performed using some nonlinear regression methods. Then an inverse modeling is done using particle swarm optimization (PSO) algorithm with some constraints. Result includes a suitable system with bandwidth as an input and dimensions width, frequency range, length over a ground plane with a substrate thickness, dielectric loss tangent and electrical thickness as an output.