In this paper, GaN films were successfully grown on the samples of MOCVD-GaN/Al2O3 (MGA) and MOCVD-GaN/6H-SiC (MGS) by HVPE method. We compare the strain of GaN films grown on the two samples by employing various characterization techniques. The surface morphology of GaN films were characterized by field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). The variations of strain characteristic were also microscopically identified using the Z scan of Raman spectroscopy. The Raman peak (E-2) shift indicates that the stress enhanced gradually as a function of increasing the measurement depth. The strain of GaN grown on MGA sample is compressive strain, while on MGS is tensile strain. The stress of GaN films grown on MGA and MGS sample are calculated. The difference in the value of stress between calculation and measurement was interpreted. (C) 2011 Elsevier B.V. All rights reserved.