The utilization of 2D layered black phosphorus (BP) in ultraviolet (UV) optoelectronic devices has garnered significant attention due to its high hole mobility and strong light–material interaction. However, its practical applications are impeded by its low light absorption efficiency and environmental instability. To address these challenges, constructing an ionic liquid gated BP/SiC mixed-dimensional photodetector by integrating the high ultraviolet light absorption capacity of SiC with the effective electronic property modulation and surface protection of ionic liquid is suggested in this work. Remarkably, the developed device exhibits an improving photoresponsivity of 10.24 A/W at a gate voltage of −2 V and source–drain voltage of 0.5 V, which is ∼73 times larger than that of the BP UV photodetector, as well as an enhanced environmental stability for at least 30 days. This research offers potential strategies for optimizing the performance of advanced functional devices using 2D/3D mixed-dimensional heterojunctions.