Graphene oxide (GO) membranes with GO sheets of different sizes were prepared on porous nylon substrates. X-ray diffraction and Fourier transform infrared spectroscopy were employed to explore the size effect of GO sheets on the microstructure of GO membranes. Field emission scanning electron microscopy was utilized to observe the membrane morphology and thickness. The effects of GO sheets, membrane thickness, draw solution concentration, and solvent parameters on organic solvent forward osmosis (OSFO) performances were studied in methanol solution. Using pure methanol as the feed solution and 1 M citric acid methanol solution as the draw solution, a 240 nm thick highly laminated GO (HLGO) membrane achieves 4.18 L m(-2) h(-1) methanol flux with a moderate reverse solute flux. In the enrichment of target products via the OSFO of HLGO membranes, model solutes and atorvastatin calcium were, respectively, employed as target molecules. The solutions containing target products could be successfully concentrated with high solvent fluxes and ideal rejection rates.