摘要： Graphene oxide (GO) is known to have some unique properties for various applications. GO is the oxidation form of graphene. It is synthesized from graphite through chemical oxidation. In this research, GO was prepared by using an Improved Hummers’ method from natural graphite powder. In addition, the effects of different reaction time of 12 hours, 24 hours, 48 hours and 72 hours on the GO were studied. Results indicated that different sample sizes of GO possessed different morphologies, attachment of functional groups and absorption peaks in Ultraviolet-Visible (UV-Vis) spectroscopy. GO was characterized by using a Scanning Electron Microscope (SEM), Fourier Transform Infrared (FTIR) spectroscopy, UV-Vis and X-Ray Diffraction (XRD). SEM result showed that the GO were appeared in a platelet-like form as compared with the GO (24 hours) where wrinkled and layered-flakes were seen and crumpled structures were seen on GO (72 hours) surface respectively. In FTIR results, the presence of oxygen-containing functional groups was confirmed in GO (72 hours) as compared with GO (12 hours) where the amount of oxygen-containing functional groups was less. In UV-Vis results, the absorption peak of GO (72 hours) was increased due to the longer oxidation time. By comparing these results, the oxidation of graphite to form GO can be determined accurately. Therefore, this study is a great benefit to provide information for researchers to synthesize high quality of GO for various applications.