The soil phase-state hydrocarbon determination method, a new method for determininghydrocarbon, has been described in this paper. Being a specific technique, this method only selec-tively extracts light carbon components which were captured during the percolation of oil and gasaccumulations and are now preserved in migration passageways, wall rocks and various secondaryminerals of near-surface soils and existent in a "cave-filling" state. The "cave-filling"state hydro-carbon is a cumulative index which will not be affected by such factors as outside temperatureand water percolation and will be kept rather firmly; hence the results of determination areexpected to be fairly stable. The phase-state hydrocarbon method Obviates the interference of bio-genic hydrocarbon, syngenetic hydrocarbon of minerals and carbonates that exists in the method ofacidolyais of hydrocarbon, raises the signal-to-noise ratio of the determination index, makesprominant useful anomalies. The method was successfully tested in two known oil-gas fields withina thick loess cover area and in an Oil-gas field with well-developed faults and covered witheolian sand, indicating that the phase-state method is superior to the method of acidolysis ofhydrocarbon.