Neodymium-doped gadolinium gallium garnet (Nd∶GGG)crystal is the best operation material of solid-state heat-capacity laser. In the present paper, Nd∶GGG single crystal was grown by Czochralski (Cz)method. Fluorescence spectra and absorption spectra were measured. At the same time, the spectral parameters of Nd∶GGG laser crystal were calculated by Judd-Ofelt theory, including absorption and emission cross-section, intensity parameters, radiative transition probability, fluorescence branch ratio and fluorescent lifetime. According to the measurement and calculation of absorption spectra, it is illustrated that the main absorption peak of Nd∶GGG crystal was at near 808 nm, the absorption cross section of the main peak at 808 nm σabs was equal to 4.35×10-20 cm2. The FWHM of absorption line-width was equal to 8 nm, and the absorption intensity became stronger with the increase in Nd3+ ions concentration. According to the measurement and calculation of fluorescence spectra, the fluorescence emission peak was at near 1 062 nm, which corresponds to 4F3/2-4I11/2 emission band of Nd3+ ions. The radiative transition probabilityof the main emission peak at 1 062 nm AJJ′ was equal to 1 832.01 s-1. The fluorescence branch ratio βJJ was equal to 45.07％. The fluorescence lifetime τ was equal to 250 μs. The stimulated emission cross section σ(λ) was equal to 21.58×10-20 cm2. The laser operation of 4F3/2-4I11/2 transition can be realized due to the larger fluorescence branch ratio and stimulated emission cross section.