Abstract: Graphene is widely used in photodetection because of its high carrier mobility and wide spectral absorption range. However, its high dark current caused by its low light absorption severely limits its performance. Molybdenum dihalide (MoX₂, X= S, Se and Te) has a high absorption coefficient, which can compensate for the high dark current in graphene-based photodetectors and result in outstanding photoelectronic properties of those based on a graphene/MoX₂ van der Waals heterostructure (vdWH). In this review, we firstly review working principles, performance indicators, and structures of photodetectors. After that, the significance of graphene/MoX₂ vdWH photodetectors is highlighted from the fundamental perspective. Preparation methodologies and performance enhancement strategies of graphene/MoX₂ vdWH photodetectors are correspondingly summarized. In the end, we highlight the current challenges and future directions of the graphene/MoX₂ vdWH photodetectors. This review will guide the design of high-performance vdWH photodetectors.