The present invention provides a graphene-cuprous oxide quantum dot photodetector and preparation method thereof, wherein the graphene-cuprous oxide quantum dot photodetector comprise a copper substrate, a cuprous oxide layer, a graphene layer and an ohmic contact electrode. The cuprous oxide layer is positioned between the copper substrate and the graphene layer. The ohmic contact electrode is arranged on the surface of the graphene layer. According to the invetntion, copper is adopted as that substrate of graphene, Cuprous oxide layer is used as light absorbing surface to realize photoelectric signal conversion, and graphene layer, cuprous oxide layer and copper substrate all have good flexibility and electrical properties, and have good compatibility with the existing integrated circuitprocess, at the same time, it has the potential to be applied to electronic equipment which may have large deformation, such as flexible wearable electronic equipment.