Abstract: The morphologies and properties of nano-montmorillonite (MMT)/hydrogenated acrylonitrile butadiene rubber (HNBR) composites fabricated via supercritical carbon dioxide (scCO₂) technology and single-handed melt mixing respectively were compared, and the effects of scCO₂ processing was examined. The effect of scCO₂ processing condition on the dispersion of MMT particles was also investigated. The results of XRD and TEM reveal the effectiveness of scCO₂ method in the HNBR composites. ScCO₂ processing facilitates the intercalation of rubber molecules into MMT galleries and the interlayer distance reaches 3.93 nm. Meanwhile, the MMT platelets are homogeneously dispersed in the matrices, and the degree of stripping is high. The temperature and pressure of scCO₂ processing almost have no effect on MMT dispersion. Compared with original HNBR, the tensile strength of composite obviously improves from 14.4 MPa to 16.3 MPa (melt mixing method) and 19.6 MPa (scCO₂ method) respectively, and elongation at break increases slightly. The composite obtained via scCO₂ method possesses higher mechanical performances, and it can also maintain good mechanical performances before or after immersed in corrosive medium.