Abstract: To evaluate the accuracy of the commonly used method based on thermogravimetric analysis in calculation of the thermal kinetic parameters, particulate matter (PM) was sampled at different engine loads and pre-treated in N<sub<2</sub< atmosphere. Indirect evaluation on the influence of pre-treatment on PM kinetic parameters was made based on the analysis of microstructure morphology and nanostructure parameters. Onion-like structures of raw PM and PM aggregation sampled at 80% engine load converted to core-shell like structures, however, it was almost no change for raw PM sampled at 100% load. The diameter of raw PM sampled at 80% load decreased greatly. The mean lattice fringe separation distance decreased for all the three samples and raw PM sampled at 80% load had the largest decrease. For PM aggregation sampled at 80% load and raw PM sampled at 100% load, the mean fringe length changed slightly and mean fringe tortuosity increased greatly, while it was the opposite for raw PM sampled at 80% load. The analysis indicated indirectly that the thermal kinetic parameters of pre-treated samples was different from raw samples.