Simulation and prediction of the thermo-mechanical behavior of composites based on thermoplastic polymers do not cease arousing the interest of a wide range of manufacturers in the automotive industry, for instance. Therefore, the determination of mechanical behavior laws must be the most efficient as possible. The key parameter to take into account is the microstructure evolution of the polymers during the mechanical solicitation [1-6]. This paper focuses on the characterization of the irreversible microstructural mechanisms involved during plastic deformation stage of uniaxial stretching tests. The matrix material of the study is the isotactic polypropylene (iPP) declined in various forms: a neat iPP, an impact iPP(PP/EPR) and two PP/EPR composites filled with mineral particles (µ-talc and CaCO3). The various compositions of these materials allow highlighting the competition between the macromolecular chains orientation mechanism and the volume damage process. Raman spectroscopy analyses are performed in real time during the mechanical solicitation using the VidéoTraction™ system [2, 5-7]. This innovative coupling system enables to follow the evolutions of the different studied composites microstructures. Results brought by Raman spectroscopy are correlated with others common analyses techniques such as in situ Wide Angle X-ray Scattering (performed with high energy synchrotron radiation on the P07 beamline at PETRAIII, Hamburg, Germany), in situ Incoherent Steady Light Transport and in situ Scanning Electron Microscopy observations.