Original and nonthermal plasma treated particulate matters (PM) samples of a diesel were obtained and characterized by Raman spectroscopy. A five-bands model was adopted for Raman spectrum curve fitting. As parameters involving most information about carbon structure, variation of FWHM of D1 band and D3 relative intensity were analyzed. It was found that original PM presented higher graphical structural order and lower chemical heterogeneity with the increase in the diesel load. After the treatment of NTP, the graphical structural order and chemical heterogeneity of PM kept at a relative stable level, affected very slightly by diesel load. Meanwhile, the amount of molecular carbon in PM increased. Further study for relation between structural evolution and chemical reactivity of PM with chemical kinetics would make Raman spectroscopy of great promise to become an important method for PM characterization, which could provide basis for more effective removal.