Highly sensitivity Surface Plasmon resonance (SPR) sensor consisting of Ag-Pt bimetallic films sandwiched with 2D materials Black Phosphorus (BP) and Graphene over Pt layer in Kretschmann configuration is analyzed theoretically using the Transfer Matrix Method. Numerical results shows that upon suitable optimization of thickness of Ag-Pt and number of layers of BP & graphene, sensitivity as high as 412º/RIU can be achieved for p-polarized light of wavelength 633 nm. This performance can be tuned and controlled by changing the number of layers of BP and graphene. Further, the addition of graphene and heterostructures of black phosphorus not only improved the sensitivity of the sensor but keep the FWHM of the resonance curve much smaller than the conventional sensor utilizing Au as plasmon metal and hence improved the resolution to a significant extent. We expect that this new proposed design will be useful for medical diagnosis, biomolecular detection and chemical examination.