A graphene/silicon-quantum-dots (Si-QDs)/Si Schottky-PN cascade heterojunction is proposed and demonstrated for high-performance short-wavelength infrared (SWIR, 1–3 μm) photodetection. The heterojunction integrates a graphene/Si Schottky contact and a Si-QDs/Si PN junction in a cascade structure, leveraging the broadband light absorption of graphene and Si-QDs, as well as the efficient carrier separation/transport of the Schottky-PN cascade configuration. Si-QDs are synthesized via plasma-enhanced chemical vapor deposition (PECVD) and embedded between graphene and the Si substrate, enabling strong absorption in the SWIR region through quantum confinement effects. The fabricated photodetector exhibits a responsivity of 8.2 mA/W at 1.55 μm (telecom wavelength), a specific detectivity (D*) of 1.1×10¹⁰ Jones, and a fast response speed (rise/fall time) of 2.3/3.1 μs. Moreover, the device shows excellent stability under ambient conditions without encapsulation, attributed to the protective role of graphene and the passivation effect of Si-QDs. This work provides a feasible approach for developing low-cost, high-performance SWIR photodetectors based on silicon-compatible materials, promising applications in optical communication, remote sensing, and environmental monitoring.