A novel size-controllable germanium quantum dot (Ge QD) is synthesized and decorated onto reduced graphene oxide (RGO) fragments to overcome the low infrared (IR) photoresponses (∼0.1 A/W)13,14 of pristine graphene. With the integration of flexible substrate, monolayer graphene (MLG) electrode and n-type zinc oxide (ZnO), a high-performance QD-decorated-RGO/ZnO heterostructure infrared photodetector is reported in this study. The Ge QD-decorated-RGO hybrid photosensitive composite improves the responsivity (∼9.7 A/W, 1400 nm) in IR waveband without sacrificing the response speed (∼40 μs rise time and 90 μs recovery time). In addition, the effective barrier formed between graphene and ZnO interface restricts the dark current (∼1.4 nA, -3 V) to guarantee the relatively excellent rectifying behavior and high on/off ratio (∼10(3)) for this IR photodetector. With these superior inherent properties and micron-sized sensing active area, this photodetector manifests great potential in the future application of graphene-based IR photodetector.