A key technique of nano-integrated optics is the development of novel and highly efficient nano-scale waveguide devices. As a basic optical splitting and light-connecting device, nano-scale Y-branch waveguide is the basis of designing and developing nano-scale optical devices. A novel Y-branch waveguide based on surface plasmon polaritons (SPPs) is proposed for high integration, and the finite-difference time-domain (FDTD) method is used to study its propagation properties. The simulation results show that the proposed Y-branch waveguide realizes optical splitting with large splitting angle in the optical communication band, and the transmission efficiency is still over 92.8% for 180° splitting angle. Besides, it is characterized by its nano-scale size, guiding wave with good performance being insensitive to the defect at the joint of the splitter, and large tolerance. The study of the novel waveguide devices can offer some valuable guidances to the research and application of nano-integration devices.