The invention discloses a fractal-element-based frequency selective surface structure which comprises a first frequency selective surface layer and a first dielectric plate, wherein the first frequency selective surface layer comprises a plurality of patch elements; each patch element comprises a first fractal ring, a second fractal ring, a third fractal ring and a fourth fractal ring; the first fractal ring is a regular triangle ring; each side is provided with a U-shape bending part; the second fractal ring, the third fractal ring and the fourth fractal ring are located in the regular triangle ring and are in rotational symmetry distribution about the center of the regular triangle ring; the second fractal ring, the third fractal ring and the fourth fractal ring are quadrangle rings; the first vertex angle, the second vertex angle and the third vertex angle are 120 degrees, 90 degrees and 90 degrees in sequence; the fourth vertex angle is opposite to the first vertex angle; and two sides of the fourth vertex angle are provided with the U-shaped bending parts respectively. The frequency selective surface structure disclosed by the invention has good polarization stability; and the wave-transmitting characteristic can be effectively improved on the basis of keeping the wave-absorbing characteristic. Furthermore, the invention further discloses a frequency selective surface structure-based window absorber.