Abstract: GaN single crystals were prepared by Na-flux LPE method on the GaN/Sapphire substrates,the influence of pressure on the GaN crystal growth speed was explored,the samples were characterized by DCXRD,it was found that under the conditions of the N2 pressure of 3.8MPa and the temporature of 800 ℃,the epitaxial layer showed well crystalline quality and higher growth speed.The study also found that the growth rate of the GaN epitaxial layer is not only concerned with the N transport in the solution,but also with the concentration of N in the melt.