A nuclear microprobe with high spatial resolution and high analytical sensitivity was applied to analyze trace elements, especially lead, in vehicle exhaust of Shanghai city. The result shows that the chemical composition and its corresponding x-ray relative intensity are different among different vehicle exhausts, There are many kinds of metal elements in particles of vehicle exhaust, most are harmful to people, such as Ti, Cr, Mn, Pb, etc. We found that the lead concentration was 6820μg/g and the bromine concentration was 5300 μg/g in the exhaust from Santana using leaded gasoline (SULG), which is higher than any other kinds of vehicle exhausts. We have also detected the minimum lead in the particles of unleaded gasoline and its content varies from one to another. Its mean concentration was 450 µg/g and the highest reached 6210 µg/g. The unleaded gasoline's Pb existed in the whole particle while the leaded gasoline's enriched in the surface of the particle and was more harmful to the human beings.