We propose a miniaturized-element frequency selective surface (MEFSS) by using the coupling mechanisms between capacitive surface and inductive surface, so the uint cell size will not be restricted by wavelength. In order to improve resonance stability performance with respect to different polarizations and incidence angles, according to the traditional FSS Y element, we create periodic elements of capacitive surface and inductive surface with Y shape and Y element array is in the form of equilateral triangle, The grid array and the effects of the parameteristics of Y loop element on the frequency response characteristics of MEFSS are calculated using the modal matching method. With filming technology and lithography, the corresponding capacitive surface and inductive surface between polyimide are produced and a prototype MEFFSS using freedom space method is examined. Both simulated and measured results obtained show that the MEFFSS constructed by using equilateral triangle Y element array has much better f0 resonance stability performance with respect to different polarizations and 60 incidence angles, and the -3 dB bandwidth reaches up to 7.6 GHz. We present a theoretical and experimental reference of MEFSS for the applications in large-angle incidence curved streamlined radome.