As the gallium volatilization is effectively inhibited by designing suitable temperature field structure and optimizing the growth atmosphere, a diameter of 3 inches Gd3Ga5O12 (GGG) crystal with high quality is successfully grown by Czochralski method with the combining of raw material pretreatment and necking technology. And the crystal structure, crystalline quality, dislocation morphology and transmission spectrum are investigated in detail. The X-ray diffraction (XRD) shows that the as-grown crystal is single phase and the lattice constant is 1.2379 nm. The X-ray rocking curve (XRC) exhibits that the crystal possesses high crystalline quality. The surface roughness of (111) crystal surface is measured to be about 0.203 nm by atomic force microscopy (AFM). The dislocation corrosion pits on the crystal surface (111) are observed and analyzed, and it shows that the dislocation density ranges from 28 /cm2 to 85 /cm2. The transmission spectrum indicates that the crystal has wide transmittance band and the Sellmeier equation coefficients are fitted. All the results indicate that the 3 inches GGG crystal can be applied as the substrate material of the magneto-optical epitaxial film and laser host, and larger-size crystal can effectively improve the utilization efficiency and homogeneity.