The present invention discloses a visible near-infrared ultra-broadband absorber and its preparation method, comprising a substrate and a five-layer optical film, wherein the bottom film is a bottom metal absorbing layer; a top germanium layer is provided on the top of the bottom metal absorbing layer; and remaining three layers are provided on the top of the top germanium layer with gradually decreasing refractive indexes from the bottom to the top. The present invention is based on the blocking effect of the metal absorbing layer and broadband anti-reflection film stack of the germanium layer, which has realized visible near-infrared ultra-broadband absorption with high efficiency and good angle insensitivity, and has fully surpassed traditional absorbers in terms of performances. Compared with conventional broadband absorbers and artificial electromagnetic absorbers proposed in recent years, the compact multilayer film structure in the present invention is simpler and avoids complicated nano-fabrication techniques. Therefore, it can significantly reduce production cost and shorten the production cycle, and is thus suitable for large-scale mass production.