This paper reports the high mobility InN film grown by MOCVD with GaN buffer layer on sapphire substrates. Different buffer layers are used in our experiments. These buffer layers included the annealing sapphire substrate, the low-temperature GaN layer (LT-GaN), the high-temperature GaN layer (HT-GaN) and the complex buffer layer with HT-GaN on LT-GaN. The crystalline quality of the InN film is sensitive to the underlying buffer layer when the film is grown under the high effect V/III ratio condition. And the growth conditions are optimized in our system. We employed the three-step buffer layer with HT-GaN and LT-GaN on annealing sapphire. The mirror like layers on 2 in sapphire wafers was obtained. The structure, optical and electrical characteristics of InN was investigated by Xray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), photoluminescence (PL) and IR optical absorption. The PL and the absorption studies of the materials reveal a marked energy band gaps structure around 0.70 eV, at room temperature. The uniformity of morphology and the electrical property of the grown InN film are markedly improved by using the complex buffer layer with HT-GaN and LT-GaN on the annealing sapphire. The InN film grown by this buffer layer has the carrier concentration of 3.9 x 10(18) cm(-3) and the Hall mobility of 939 cm(2)/Vs. (c) 2006 Elsevier B.V. All rights reserved.