Strong coupling between electronic transitions and localized optical modes can yield a new kind of optical source,which is important.It would break the bottleneck of delivering light from a macroscopic external sourc e to the nanometre scale,such as low coupling efficiency and difficulty in accessi ng individual optical modes.With metal nanoparticle dimer as an optical resonance cavity, we simulate a novel localized surface plasmon laser by using the finit e difference time-domain (FDTD) method.Lorentz permittivity model is applied to study the properties of the gain medium of the dimer,where the interaction mecha nism between the two individual nanoparticles is investigated.Furthermore,we explo re the influence of localized surface plasmon resonance interaction on the enhancem ent of local field.The simulation results show that the dimer surface plasmon laser can enhance the local electric field significantly with a maximum of 27times higher than the single nanoparticle surface plasmon laser for the enhancement factor Q.This research may lay foundation for the design of nano-optics,especia lly laser devices.