Effect of petroleum hydrocarbon in soil on soybean physiological indices was studied by pot experiments. The results indicate that, when the petroleum hydrocarbon quality in soil is below 5 000 mg·kg-1, soybean seedling chlorophyll content,nitrate reductase activity and SOD activity all rise first and then decline, but near 5 000 mg·kg-1,these indices have no obvious decline. When petroleum hydrocarbon quality is 8 000 ~10 000 mg/kg, chlorophyll content, SOD activity and nitrate reductase activity have shar...