In this paper, we report on the fabrication of planar waveguides in z-cut Nd:SGG crystals, using $500\mathrm{keV}$ He ion implantation with fluences of $3\times {10}^{16}\text{ions}/{\mathrm{cm}}^2$ at $77\mathrm{K}$ $1\times {10}^{16}\text{ions}/{\mathrm{cm}}^2$ at room temperature, annealed at $260°\mathrm{C}$ for $30\min$ . The guiding modes of the planar waveguides were measured by the prism-coupling method at $633\mathrm{nm}$ . The near-field intensity distribution and propagation loss of the light in the waveguides were measured by the end-fire coupling method. The absorption spectra were also measured. The refractive index profile was reconstructed using the intensity calculation method, and the light propagation mode was simulated with the finite-difference beam propagation method. The calculated results were in good agreement with the measured waveguide modes, indicating the feasibility of these designable devices.