A novel plasmon polariton nanolens formed by two subwavelength metal slits surrounded by surface dielectric gratings is proposed and demonstrated numerically.The dispersion characteristics of surface plasmon polaritons (SPPs) in a metal waveguide are studied by using genetic algorithm, which shows that the effective index can be adjusted effectively by changing the widths and dielectric constants of these slits, and the propagation of SPPs can be controlled further.By combining the Finite-difference Time-domain (FDTD) method with Perfect-matching Layer (PML) absorbing boundary conditions,the distribution of optical field in the lens structure is simulated and the effect of number of surface gratings on imaging characteristics is discussed.Experiments show that the focal length and width are increased with the increase of number of the surface gratings.When the number of the surface gratings increases from 5 to 11, the focal length increases from 1.715 μm to 2.325 μm and the focal width increases from 0.615 μm to 1.715 μm.Results show that this lens structure can be availabe for the future integrated optics.