Abstract: In this paper, a novel hybrid plasmonic nanolaser with a metal ridge and a MgF2 dielectric layer at ultraviolet band is demonstrated. The electric field distribution, the modal properties, the quality factor and the lasing threshold are investigated by using the finite-element method on the basis of the COMSOL Multiphysics platform. At the 390 nm working wavelength, the structure of the nanolaser can reach good deep-subwavelength mode confinement by optimizing its geometric parameters, while maintaining high quality factor and low propagation loss and low gain threshold. Compared to the previously reported structure with a metal plate, this structure has stronger capacity of field confinement and microcavity bound with the same geometric parameters. The structure shows potential to promote miniaturization and integration of lasers.