With MgO and Fe2O3 doped into LiNbO3 ,the Mg: Fe: LiNbO3 crystal was grown. The highest exponential gain coefficient (r=80cm-1 ) was measured in a thin Mg :Fe: LiNbO3 sample,of which the thickness was 0. 2mm. The sample showed high gain coefficient within a wide angular range. These features were explained by the effect of light crawling, which originated from light scattering with large angles. The response speed and the ability of anti-scattering of Mg:Fe:LiNbO3 were improved as compased with Fe:LiNbO3. The once iteration of output in real-time holographic associative memory was implemented by using Mg:Fe:LiNbO3 as a photorefractive amplifier.