In this paper, an automatic design procedure for microstrip equalizers is presented based on least-squares Monte Carlo (LSM) method. Firstly, three types of microstrip resonators, the resistor-loaded open stub, resistor-loaded shorted stub, and the parallel coupled line, are analyzed in the microwave frequency band. Then, the three types of resonators are combined to design microstrip equalizers with positive/ negative slopes and a prescribed gain curve based on LSM algorithm. The simulated and measured results are consistent well with each other in the frequency band of 0–18 GHz, which demonstrates the validity of the automatic design procedure.