This work is to develop a novel nanocomposites with high gas barrier properties. The permeability is reduced by aligning the magnetic nanoplatelets into a highly oriented manner in brominated butyl rubber (BIIR) latex via a low magnetic field. Iron oxide (Fe3O4) nanoparticles were deposited on the surface of montmorillonites (MMTs) modified with gamma-aminopropyltriethoxysilane (APTES) and octadecyl trimethyl ammonium bromide (OTAB) to produce m-OMMTs nanocomposites. The morphology and microstructures of the prepared m-OMMTs and m-OMMTs/BIIR highly ordered nanocomposites were characterized by X-ray power diffraction (XRD), Fourier Transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and transmission electron microscope (TEM). Systematic characterization demonstrated that APTES was chemically bonded onto MMTs and Fe3O4 nanoparticles and further confirmed the bond formation between Fe3O4 and MMTs platelets, which could ensure the adhesion between the Fe3O4 nanoparticles and MMT platelets. The modified magnetic MMT nanoplatelets (m-OMMTs) were added into BIIR latex and aligned in a low magnetic field T-m = 80 mT. Besides, a ellipsoidal shell model was presented to estimate the minimum magnetic field strength for aligning m-OMMTs in BIIR latex. Finally, the helium permeability measurements were performed by GDP-C gas permeation apparatus. It can be observed that the new method was proved very useful to align m-OMMTs embedded in polymer matrix leading to a highly ordered composite with excellent gas barrier properties.