Abstract: Based on the vertical micro migration theory of hydrocarbons,the geochemical exploration technology detects trace hydrocarbon components by advanced instruments and devices.Different grades of anomalies all have the character of good reproducibility and high stability.Regional anomalies forecast the petroleum prospects of a basin,zone anomalies point out the favorable zones of hydrocarbon enrichment,local anomalies provide basis for trap evaluation or the arrangement of trap drilling,and mineral distribution anomalies indicate the extension outside-border direction of oil and gas fields.Downhole geochemical exploration can predict hydrocarbon reservoirs while drilling and give oil-testing horizons.All above functions of geochemical exploration were discussed by practical exploration examples.It was considered that confusing prospecting stages,being eager for quick success and instant benefit,ignoring applied basic research and insufficient personnel technical forces which existed in hydrocarbon geochemical exploration at present were questions restricting the development of hydrocarbon geochemical exploration technologies.