The invention discloses a broadband mirror comprising a substrate layer, a metal reflective layer and a photonic crystal reflective layer arranged in order from bottom to top, wherein the photonic crystal reflective layer is a one-dimensional photonic crystal and comprises a first photonic crystal layer, a second photonic crystal layer and a third photonic crystal layer arranged in sequence from bottom up; the center wavelength of a photonic band gap of the first photonic crystal layer is 300nm, the center wavelength of a photonic band gap of the second photonic crystal layer is 340nm, and thecenter wavelength of a photonic band gap of the third photonic crystal layer is 380nm. The broadband mirror has an ultra-wide reflection bandwidth and high reflectivity, greatly reduces the number ofcoating layers and reduces the internal stress of the film layer.