Abstract: Aiming at the requirement of stealth aircraft antenna, especially the specification for L-band broadband antenna array, it is needed to design a stealth radome with ultra-thin and wideband frequency selectivity surface (FSS) for working in L-band. Due to the low working frequency and wide bandwidth, the traditional design method will make the radome thickness thicker, which is hard to apply in practice. Taking broadband and low profile into consideration, this paper proposes a cascade sub-wavelength structure based on new orthogonal separation metal strip inductance layer, square ring capacitance layer and magnetic materials. At last, a broadband and low profile FSS with 0.035λ thickness of and 28.6% relative bandwidth is designed by means of genetic algorithm.