Abstract: Long chain branching polypropylene (LCB-PP)/organomontmorillonite (OMMT) nanocomposites were prepared in a twin-screw extruder via a melt-blending method, and their microstructures, rheology and mechanical properties were investigated. The results of transmission electron microscopy (TEM) showed that the clay layers were mostly exfoliated in the LCB-PP matrix. Rheology test results showed that when the clay loading reached a threshold value, the nanocomposite exhibited an increased storage modulus at low frequency and more obvious shear-shinning behavior, indicating that a compact and stable network structure formed and hindered macromolecular chain relaxation and mobility. The results of mechanical property test showed that the addition of OMMT improved the tensile strength, notched impact strength, and flexural modulus of LCB-PP, but reduced its flexural strength.