Highly efficient near- and medium-wave infrared detection at room temperature is considered one of the most intensive studies due to the robust detection under foggy weather or other low visibility conditions. 2D atomic layer graphene has an unconventional broad optical spectrum and high electron or hole mobility properties for next-generation electronic and optoelectronic devices. Single-layer graphene has a lower quantum efficiency, and PbSe has a direct narrow bandgap with a highly sensitive infrared response. Here, we examine the growth mechanism of high-quality oriented (200) PbSe crystals on single atomic layer graphene using the electrochemical atomic layer epitaxy (ECALE) method in an aqueous electrolyte. The crystalline phase and density of nucleating seeds controlled by adjusting the electrodeposition parameters are crucial for determining the submicron-crystal geometry. It is revealed that the controllable growth orientation and nucleation of PbSe crystals are realized by combining the underpotential deposition (UPD) of Pb and the overpotential deposition (OPD) of Se. The PbSe crystal/graphene hybrid photodetector indicates the benefit of infrared absorption. An extraordinary response speed of 1.8 ms, a photo-responsivity exceeding 36 A W⁻¹, and a figure-of-merit detectivity of D* > 2.7 × 10⁹ Jones have been demonstrated at 2.7 μm and room temperature, demonstrating its potential for practical optical and optoelectronic applications.