In this paper, a simulation-based optimization technique for integrated circuit (IC) design automation is presented. Based on a genetic algorithm (GA), Levenberg-Marquardt (LM) method, and circuit simulator, a window-interfaced prototype of computer-aided design (CAD) is developed for IC design. Considering low noise amplifier (LNA) IC, we simultaneously evaluate specifications including S parameters, K factor, noise figure, and input third-order intercept point in the optimization process. If the simulated results meet the aforementioned constraints, the prototype outputs the optimized parameters. Otherwise, CAD activates GA for global optimization; simultaneously, LM method searches solutions with the results of GA. The prototype then calls a circuit simulator to compute and evaluate newer results until all specifications are matched. More than fifteen parameters including device sizes, passive components, and biasing conditions are optimized for the aforementioned constraints. For LNA IC with 0.18pm metal-oxide-silicon filed effect transistors, benchmark results confirm the functionality of the implemented prototype.