The optically polished LiNbO3 crystal was implanted with 3.0 MeV nickel ions to a dose of 8 × 10T14 ions/cm2. The implanted sample was orderly annealed at different temperatures for different times in air ambient. The waveguide properties before and after annealing were investigated. Dark modes were observed by the prism coupling technique. The reconstructed refractive index profiles were obtained with the reflectivity calculation method.