We investigate the optical properties of Nd: YAG crystals grown by temperature gradient technology with different Nd doping levels. The Nd concentrations used are 1.0, 1.5, 2.0, 2.5 and 3.0at.%. It is found that the absorption coefficients of Nd: YA G crystals increase with increasing Nd concentrations. The absorption coefficient of 3.0 at. %Nd:YAG is up to 22.1 cm-1. The laser performance of these Nd:YAG crystals is compared with that of the traditional Nd:YAG (1.1 at.% Nd) grown by the Czochralski (CZ) method. Although concentration quenching exists in highly doped Nd: YAG, 2.0 at. % Nd:YAG shows excellent performance with the slope efficiency of 46.7%,which is higher than that (39%) of 1.1 at.% Nd:YAG grown by the CZ method.