In this study, the effect of addition Calcium carbonate (CaCO3) filler component on solid state thermal decomposition procedures of Polypropylene-Low Density Polyethylene (PP-LDPE; 90/10 wt%) blends involving different amounts (5, 10, 20 wt%) Calcium carbonate (CaCO3) was investigated using thermogravimetry in dynamic nitrogen atmosphere at different heating rates. An integral composite procedure involving the integral iso-conversional methods such as the Tang (TM), the Kissinger-Akahira-Sunose method (KAS), the Flynn-Wall-Ozawa (FWO), an integral method such as Coats-Redfern (CR) and master plots method were employed to determine the kinetic model and kinetic parameters of the decomposition processes under non-isothermal conditions. The Iso-conversional methods indicated that the thermal decomposition reaction should conform to single reaction model. The results of the integral composite procedures of TG data at various heating rates suggested that thermal processes of PP-LDPE-CaCO3 composites involving different amounts of CaCO3 filler component (5, 10, 20 wt%) followed a single step with approximate activation energies of 226.7, 248.9, and 252.0 kJ.mol- 1 according to the FWO method, respectively and those of 231.3, 240.1 and 243.0 kJ mol- 1 at 5 degrees C min- 1 according to the Coats-Redfern method, the reaction mechanisms of all the composites was described from the master plots methods and are Pn model for composite C-1, Rn model for composites C-2 and C-3, respectively. It was found that the thermal stability, activation energy and thermal decomposition process changed by the increasing CaCO3 filler weight in composite structure.