The intrinsic field of the waveguide by numeric solution is calculated. The mathematical model of bend waveguide refractive index is given. The curved optical waveguide is calculated analyzed with FDTD. By numeric calculation, the evolution of the pulse entering the bend waveguide, the pulse propagating in bend waveguide and its energy loss in the condition of different bend radius are obtained. The smaller the bend radius is, the more noticeable of the pulse moves and deforms, the more serious the energy loss. The bended waveguide is widely used to integrate optics and optical detection. etc.