The objective of this research was to prepare natural rubber/methyl methacrylate copolymer membrane for used in lubricating oil separation. The graft copolymerizations of Polymethyl methacrylate on NR (NR-g-PMMA) was prepared by emulsion polymerization process. Fourier transform infrared spectroscopy (FT-IR) and graft efficiency was used to verify the modified products. NR-g-PMMA latex was vulcanized with sulfur. Casting films of NR-g-PMMA were cured at 115 ํC for 10 min. NR-g-PMMA films were prepared with various ratios of the components. The effect of ratio of PMMA on the properties of film were studied i.e., film forming by specific appearance, surface of films by scanning electron microscope (SEM), durability in hexane and lubricating oil by swelling method, transportation properties by gravimetric sorption. The used lubricating oil was separated by dialysis process. The effect of concentration of initial oil to dialysate oil, osmosis volume, and percent dialysate oil were studied. Finally, the chemical and physical properties of the dialysate oil were compared with re-refined base oil standard of Thailand Industry Standard Institute. The study showed that the amount of PMMA had affected on quality of films. It was found that at high ratio of PMMA to NR more than 22.5% of film exhibited the decrease of film forming ability. Increasing of the ratio of PMMA to NR induced the roughness surface of film. The durability in solvent was improved. The transportation properties showed in term of diffusion coefficient (D) and permeability coefficient (P) were higher and varied with the roughness of surface. The transport mechanism of film was anomalous-type diffusion. The ratio of PMMA: NR vulcanized with sulfur membrane that suitable for membrane separation process was at 31.69 the dialysis process indicated that the concentration was proportional to dialysate oil and osmosis volume, but inverse proportional with percentage of dialysate oil. The chemicals and physicals properties of dialysate oil showed that the contaminant could be reduced by 70-80%. The oil recovery was 75%. When percolation oil through caustic-treated clay and pass to absorption clay, the re-refined oil met the specification of re-refined base oil standard.