Here we demonstrate the fabrication of two-dimensional plasmonic photonic crystal (PPC) nanostructures to modulate the nanocavity plasmon (NCP) mode in the scanning tunneling microscope (STM) junction. Theoretically optimized PPC structures with particular defect modes were fabricated and used as the substrates for STM induced luminescence (STML) research. Stable STM imaging and STML studies were achieved by covering a suspended graphene sheet on top of periodic PPC structures. Our preliminary STML results suggest that the NCP emission can be selectively enhanced by the defect mode of the PPC structures, which paves the way for future studies on the engineering of electrically driven single-molecule photon sources and plasmonic lasing through tuning NCP modes.