A surface plasmonic nano-laser structure based on a nanowire/gap/metal layer was proposed. The models produce a significant field enhancement effect through the mode-coupling between nanowire and metal layer. Modal properties and lasing threshold under different geometric shapes and parameters were investigated and analyzed by the finite element method. Simulation results reveal that this kind of nano-laser has a low propagation loss and high field confinement ability, its minimum propagation loss is only 0.013 3 and the minimum normalized mode area is only 0.007. The results provide theory and technique support to the field of new nano-laser design.