This study proposes a graphene monolayer/few layered Ti₃C₂T_x MXene/silver film as a new plasmonic hybrid nanostructure. The feasibility of two-dimensional Ti₃C₂T_x MXene in the ultrasensitive detection of surface plasmon resonance (SPR) was confirmed using the transfer matrix method. Calculation results show that both the photon absorption and energy loss are balanced by optimizing the thickness of Ti₃C₂T_x MXene and the silver film. In addition, under an excitation wavelength of 632.8 nm, the optimal sensing configuration is monolayer graphene/3-layered Ti₃C₂T_x MXene/35-nm silver film, which can produce an ultralow (approaching zero) SPR reflectivity (3.48×10 ^-9). For a minute variation in the refractive index (as small as 0.0012 RIU), the proposed configuration can produce a differential phase response up to 110.55°and provide a phase detection sensitivity as high as 9.21×10 ⁴ (°)/RIU. In comparison with the conventional sensing configuration with angular modulation, the proposed configuration can provide an enhancement factor that is four orders of magnitude higher. Therefore, our proposed configuration has potential application in ultrasensitive biochemical detection.