The invention relates to a wide spectrum multi-band detection structure with selective absorption enhancement and its preparation method. The structure comprises a plurality of sub-pixel units capable of detecting incident light in different bands. Each sub-pixel unit is composed of a square well-shaped microstructure array and a metal lower electrode (2), a photosensitive layer (3) and an upper electrode (4) on the surface thereof. The size and array spacing of square well-shaped microstructures in different sub-pixel units are determined according to the detection bands of the sub-pixel units where they are located. The upper openings of the square well-shaped microstructures are hollow to form a resonant cavity, and the adjacent square well-shaped microstructures in the same sub-pixel unit form a resonant cavity, thus solving the problem that the detector structure in the prior art cannot simultaneously realize visible light-near infrared multi-band absorption enhancement detection.