Abstract: In this paper, the development of equivalent circuit theory of frequency selective surface (FSS) is reviewed and the necessary conditions for its application to improve the design efficiency of FSS are analyzed. The method of design a series of band-pass, band-stop, single-band and multi-band FSS with high performance based on equivalent circuit is emphasized, which is accomplished by using the components with quasi-lumped inductance and quasi-lumped capacitance effect. The theoretical and experimental results show that these FSSs generally have very small size, good stability to oblique incident angle and different polarization, furthermore the resonant frequency, bandwidth and polarization characteristics could be controlled independently. At the same time, the analytical relationship between the element structural parameters and equivalent circuit parameters provides conditions for rapid FSS optimization, thus a whole set of efficient solutions from the construction to the optimization for FSS design is provided.