The propagation and combination of surface plasmon polaritons (SPPs) in Y- shaped metallic nanochannels are investigated numerically via finite difference time domain (FDTD). It is shown that the behavior of SPPs in nano-size channels resembles that of light guiding in conventional waveguides, and SPPs can also be combined effectively with appropriately designed structures. The loss associated with metal absorption and scattering with the multiple reflections between slit openings on the bend angle are analyzed numerically. The Fabry-Perot cavity effect displayed by SPPs traveling in channels with finite length is discussed as well. (c) 2005 Optical Society of America.