The influence of modification of 80 Pen bitumen using polymer Polypropylene PP as modifier was investigated by modern analytical tools like Fourier Transform Infrared spectroscopy (FTIR), Gas Chromatography Mass Spectrometry (GCMS), Carbon, Hydrogen, Nitrogen and Sulfur Analyzer (CHNS), to understand the chemical changes in bitumen before and after modification with its effect on the rheology and morphology of the polymer modified bitumen PMB. Morphological analysis was done using field emission microscopy FESEM and atomic force microscopy (AFM). Rheology of the polymer modified bitumen PMB is strongly affected by the chemical composition, structure of the polymer, mixing time and temperature. The results obtained from FTIR and GCMS revealed that the alkenes (CC), commonly known as olefins, aliphatic unsaturated hydrocarbon and propene are the major constituent of both virgin and modified bitumen. Oxidation of PP PMB was also confirmed by the presence of carbonyl functional group around 1739 cm 1 and also by the elemental analysis of CHNS analyzer, which is one cause of increase in the hardness of PMB. The decrease in penetration value with the increase in concentration of polymer in bitumen was not only by increase in viscosity of modified bitumen but also by hardened phase separated layer of partially miscible polymer acting as sheath against penetration needle decreasing the value of penetration as observed by AFM results. From AFM results it was revealed that the increase in concentration of polymer in blend also increases the thickness of phase separated polymer layer. The higher percentage of asphaltene content in virgin bitumen, obtained by n-heptane precipitation was confirmed by presence of honey bee structured asphaltene by AFM scan result. Thus the analytical tools are helpful in understanding rheological and morphological changes brought by modification as the viscoelastic behavior of polymer modified bitumen depend on concentration of polymer used in the mix, mixing temperature, mixing time, mixing technique, solvating power of base bitumen and molecular structure of the polymer PP. Homogeneity of the blend is difficult to achieve as higher molecular weight polymer was difficult to disperse in lower molecular weight bitumen thus causing the phase separation, that influences the chemical properties or in short the rheology of the binder. It was revealed from these characterization tests on modified binder that it would enhance the mechanical properties of kept up to 3 binder when the concentration of the polymer in the blend. © 2011 IEEE.