Domestic and foreign scholars have done plenty of research work to study the application of trace elements method in oil and gas geochemical exploration and have obtained a series of achievements. There are two theoretical hypotheses can be used to explain the abnormal distribution of trace elements in surface soil over hydrocarbon reservoir, namely “the electric field theory” and “the vertical micro migration theory of hydrocarbon”. A large number of practices prove that trace elements can be transported vertically from the deep of hundreds to thousands miters to the ground surface and form geochemical halo in the soil over oil and gas reservoirs. The size of geochemical halo in surface soil is close to the vertical projection of reservoirs on the earth’s surface. Therefore, we can analyses the hydrocarbon distribution and evaluate the oil and gas potential according to the distribution characteristics of trace elements in surface soil of oil and gas field. By researching the distribution characteristics of trace elements in B horizon soil in the Lamadian oilfield, Daqing area, it shows that U and Sr are indexes elements for predictions of oil and gas. There appears low anomaly value of uranium content in surface soil over the oil reservoir and high value anomaly over the margin of it. On the contrary, strontium content shows high abnormal value in surface soil over the reservoir. According to the geochemical element anomalies in surface soil, the reservoir boundary can be determined, which suggest a new way for oil and gas exploration.