In this paper, a graphene-based equilateral triangle nanocavity is proposed and numerically investigated. The relationship between the mode characteristics and the nanocavity parameters, such as the geometry of nanocavity and the chemical potential of graphene, is systematically explored. A high-order plasmonic WGM(whispering gallery mode) with a high quality factor of 147.93 is obtained in our nanocavity with a wavelength of around 1.415 μm in free space, with a corresponding Purcell factor as high as 7.067×108. The proposed plasmonic WGM nanocavity could be a key component of the high density plasmonic integrated circuits due to its ultra-compactness and performances. In this paper, a graphene-based equilateral triangle nanocavity is proposed and numerically investigated. The relationship between the mode characteristics and the nanocavity parameters, such as the geometry of nanocavity and the chemical potential of graphene, is systematically explored. A high-order plasmonic WGM (whispering gallery mode) with a high quality factor of 147.93 is obtained in our nanocavity with a wavelength of around 1.415 μm in free space, with a corresponding Purcell factor as high as 7.067 × 108. The proposed plasmonic WGM nanocavity could be a key component of the high density plasmonic integrated circuits due to its ultra-compactness and performances.