Abstract: In this paper, a novel approach combining artificial neural network (ANN) and ge netic algorithms (GA) to analyze and design interdigital capacitor (IDC) is desc ribed. A multilayer perceptron neural network (MLPNN) is applied to describe the model of IDC. According to the engineering requirement, the dimensions of IDC c an be designed by the trained models and GA which has global searching ability. The scattering parameters of the training samples are computed by the finite di fference time domain (FDTD). This design procedure is proved to be time saving and of high accuracy.