Unlike natural polymers, most synthetic polymers can not be decomposed by microorganisms, hence the landfill approach becomes inefficient, and other plastics waste management should be found. A study of the biodegradation properties of synthetic polymers has become very important. New techniques have been developed to obtain environmentally friendly polymers. A modification of non-biodegradable synthetic polymers with a biodegradable polymer producing environmentally friendly polymers is an established technique to solve this problem. The main problem in modification of non-biodegradable synthetic polymers with biodegradable polymers is compatibility between polymers mixtures with different properties. Polypropylene (PP) is a thermoplastic polymer and difficult to be decomposed by microorganisms in environment. Despite its many commercial application, polypropylene suffers a major deficiency that is poor interaction and compatibility with other materials. The aim of this work is to improve the properties of PP as well as its biodegradability by blending with biodegradable polyester polycaprolactone (PCL). PCL is nontoxic, biodegradable polymer material and can be blended with various synthetic polymers over a wide composition range. The main problem in preparation of PP/PCL polymer blends is compatibility between polymers. In this work is presented results of thermal properties and compatibility of PP and PCL polymer blends reinforced with nano sized titan dioxide (TiO2) particles as well as effect of nTiO2 reinforcement on the thermal properties and compatibility. Titan dioxide, one of the inorganic materials with high mechanical strengths, is used as reinforcement material for polymers. The neat polymers, PP/PCL and PP/PCL (nTiO2) polymer blends were prepared by melt compounding with a twin screw extruder Rondol 21 mm LAB TWIN , the granules of the blends were compression molding in hydraulic press. The thermal properties of the neat polymers, PP/PCL and PP/PCL/nTiO2 blends are measured using the differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) techniques.