To address the issue of low content of accelerant residues at the fire site due to combustion, volatilization and site contamination, which leads to difficulties in identification. In this study, n-heptane was used to simulate the fire site environment of gasoline as an accelerant. To perform the experiments, a pipette was adopted to monitor and generate a specific number of n-heptane drops onto the surface of a pure iron plate just beneath, the n-heptane was then ignited, after the combustion was completed the iron plate was soon cooling down to room temperature at the site. The microscopic morphology and phase composition of the corrosion products, as well as the distribution of surface particles were characterized by means of scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) etc. The results showed that: Upon combustion of n-heptane, granular amorphous carbon is observed on the surface of pure iron as a result of high-temperature cracking reaction. The amount of deposited carbon is closely linked to the surface temperature of pure iron and n-heptane content at the site, and tends to accumulate at defects and nearby grain boundaries of the pure iron plate. The combustion of n-heptane creates a local oxidizing atmosphere at the accelerant interface, resulting in numerous defects on the surface of pure iron. This, in turn, promotes the flaking of the surface oxide scale. The insights gained in this study can help to identify the presence of accelerant at the fire scene.