Abstract: In this paper, a stable miniaturized band-reject frequency selective surface (FSS) is proposed. Simulation results show that the dimension of the equal-area square is only 0.057λ。×0.057λ。 and the thickness is 0.021λ。 where represents the wavelength of the resonant frequency. The arm-length and resonant length of the proposed structure was lengthened by bending arms into the inside of the unit cell to improve the space utilization and reduce the cell size. The equivalent inductance and capacitance are improved which contributes to miniaturization of unit cell爷s dimension. The proposed structure's angle stability is also improved due to the reduction of distance between unit cells. The measure and simulation results demonstrate the miniaturization characteristic is stable with respect to waves with both polarizations and different incident angles. With excellent band-reject characteristic, the proposed FSS obtains 96.3% reduction in dimension comparing with the traditional Y element.