The adsorption and fluorescence spectra of the grown Nd∶GdYAG were measured. The spectral parameters, such as oscillator strength, line strength, intensity parameter Ωt, transition probability between 4F3/2→4IJ levels, radiation lifetime, and fluorescence branching ratio, were calculated with Judd-Ofelt theory. The calculated Ωt are Ω2=(0.813±0.200)×10-20 cm2, Ω4=(3.381±0.187)×10-20 cm2, Ω6=(5.135±0.278)×10-20 cm2, respectively. Compared with Nd-doped YAG, LuAG, YVO4, and other crystals, Nd∶GdYAG crystal has a larger Ω2, showing that the addition of Gd3+increases the disorder of the host. The absorption cross-section and refractive index in the range of 300~1 200 nm were calculated and fitted. The absorption cross-section at 808 nm is 5.0×10-20 cm2. The refractive index at 1 064 nm is 1.80. The measured fluorescence lifetime of 4F3/2 level is 228 μs, which is close to the calculated radiation lifetime of 240 μs. The emission cross-section at 1 064 nm is 1.23×10-19 cm2, which is close to that of Nd∶YAG crystal. Addition, at room temperature, the thermal conductivity of Nd∶GdYAG crystal is 5.992 W/(m·K), which is slightly smaller than that of Nd∶YAG and Nd∶GGG, but larger than that of Nd∶YVO4 crystal. The results show that Nd∶GdYAG is a promising new laser crystal material.