Abstract: Soil free hydrocarbon technology is based on high-precision gas chromatography and vehicle-mounted rig sampling equipment, directly using gaseous hydrocarbons (C1-C5) in the soil into the sample analysis. This technology can solve the detection of micro-, ultra-volume hydrocarbon gas during soil gas collection and sealing, which has achieved collection, analysis and interpretation all on site and integrated. Compared to absorbed or acidextraction hydrocarbon measurement, free hydrocarbon anomaly can better reflect the movement of hydrocarbon gas in underground reservoirs, and it is less vulnerable to surface landscape and lithologic conditions. Practices of thin oil exploration in Jiergalang Depression, Inner Mongolia and shallow propecting in Dawanqi area, Xinjiang's Tarim Basin have shown that the technology has a good effect in the field of shallow oil and gas exploration. At the same time this paper has pointed out that this technology can not be used to define the absolute anomaly correlation with the oil and gas, and it can not answer how much oil and gas is enriched. In the trap evaluation or drilling survey, it's better to combine closely geochemical results with the seismic, geological and other information together to carry out a comprehensive analysis, it has been specially emphasized that there should not be any big leap of exploration stages in using geochemical data.