The thermo-oxidation behaviour of modified polypropylene nanocomposites obtained in molten state, in accelerated conditions are studied in this work. The nanocomposite were processed in twin-screw extruder, and the dumbbell samples were obtained by thermopressing. The montmorillonite clay, Cloisite 20A was added in modified polypropylene at concentractions of 0.1, 5 and 10 wt% in presence of the PP-g-MA (polypropylene-graft-maleic anhydride) as compatibilizer agent. The samples were mounted in device and placed in stove at 120 ºC with air circulation. The thermoxidative stability of the PPNCs were investigated using the characterization techniques: spectroscopic (ATR-FTIR), microscopy (SEM) and calorimetry (DSC). The oxidation induction time viewed throught carbonyl index (CI) calculation has initiated after 14 days in all the samples. The chemicrystallization effect was observed in the results of cristallinity and in the SEM images were showed more intensity of cracks in the samples with clay after 21 days of exposition.