A hybrid plasmonic microcavity consisting of a silicon microdisk which is separated from a silver toroidal strip by a low-permittivity dielectric is proposed to achieve high quality factor as well as small mode volume.Mode properties such as quality factor,effective mode volume and energy ratio have been investigated by employing a finite element method and analyzed considering the different structure geometry.Simulation results reveal that this kind of hybrid microcavity maintains low propagation loss with high quality factor ~ 7000,high field limits with small mode volume 0.315 μm3,high energy ratio and can realize a refractive index sensor with high sensitivity.