This article reported a novel technology, solid state shear milling ((SM)-M-3), to prepare poly(ethylene terephthalate)/Na+-montmorillonite nanocomposites using the pristine Na+-MMT without organic modification so as to avoid the problem that the organic modifiers, used for MMT treatment will decompose at high processing temperature of PET, and the structure and properties of the obtained samples were investigated. XRD and TEM analyses showed that Na+-MMT layers were partially delaminated and intercalated, and uniformly dispersed in the PET matrix when suffering from the strong three dimensional shearing forces of pan-milling. DSC analysis showed that Na+-MMT serves as a nucleating agent, increasing the crystallization rate as well as the crystallization temperature of PET. The properties such as thermal stability and tensile strength of the PET/Na+-MMT nanocomposites prepared by (SM)-M-3 got remarkably improved. Solid state shear milling ((SM)-M-3) method was a simple and efficient method to get polymer/Na+-MMT nanocomposites with pretty good performances without organic modification of pristine Na+-MMT. (C) 2008 Wiley Periodicals, Inc.