Synchrotron radiation photoemission spectroscopy (SRPES) is used to study the in itial growth mode of the gold deposition on the surface of GaN, the Schottky bar rier height (SBH) and the electronic structure at the interface of the Au/GaN(00 01) system. The results show that at the initial stage chemical reaction exists between the Au and GaN substrate. Over the reaction layer, the growth mode of Au deposition is 3D island mode. The SBH is examined by the SRPES and the result i s 14eV, which is consistent with other experiment reports. Analyzing the ene rgy shift of valence band and the Au core level, the interface chemical reaction is confirmed. The theoretical calculation by linear augmented plane wave method gives the density of states. According to the calculation results, the principl e of the interface reaction is discussed.