The invention discloses a two-dimensional photonic crystal composite structure enhancing broad spectrum light absorption. The composite structure is formed by compositing an absorption layer and a reflective layer. The absorption layer is in a photonic crystal structure, wherein the structure is formed by arranging a two-dimensional periodic inverted pyramid-shaped groove in the upper end face of a non-metallic material Si, and the inverted pyramid-shaped groove is filled with a polymeric film or a colloidal quantum dot film. According to the reflective layer, random pyramid grooves are arrnaged in x and y directions in the bottom end face of the non-metallic material Si, and the surface of the bottom end face is coated by a metal material Au. According to the composite structure, the absorption of p-polarized and s-polarized incident lights from ultraviolet to infrared band, and even efficient, broadband and wide-angle electromagnetic waves of a wider band is enhanced, and is beyond the Yablonovitch limit in infrared band; an electric field in the inverted pyramid-shaped groove on the surface of the absorption layer and an electric field in a cavity formed by the inverted pyramid on the surface of the absorption layer and the reflective layer are significantly enhanced; and the composite structure in particular has a great application prospect in solar cells, photodetectors, military stealth and other aspects.