In this paper, the impacts of Aromatic, Olefin and Ethanol on the formations of PAHs (poly-aromatic hydrocarbons) and VOCs (volatile organic compounds) in the gasoline engine was experimentally and numerically investigated. The objective of this study is to describe the formation process of the soot precursors including one ring to four ring benzene(A1-A4). In order to better understand the effects of the fuel properties on the formations of PAHs and VOCs, four test fuels including pure gasoline, gasoline with higher aromatics content, gasoline with higher olefin content, and gasoline with extra 10% ethanol content were experimentally studied. At the same time, these aspects were also numerically investigated in the CHEMKIN code by using premixed laminar flame model. The results showed that higher aromatics content in gasoline will lead to much higher PAHs and VOCs emissions. Similar trend was also found for the gasoline with higher olefin content, especially at higher equivalence ratios and higher engine load conditions. While the extra 10% ethanol content in gasoline has little effect on PAHs and VOCs emissions. This study indicated that reducing the aromatic and olefin contents are efficient methods in decreasing the PAHs and VOCs emissions.