Abstract: A novel method of petroleum geochemical exploration is introduced in this paper,i.e.the thermo-released analysis of AC carbonate in surface soils.AC carbonate referred here means the secondary carbonates which were derived from hydrocarbons and bought about erosion to the surface soils.Such an erosive carbonate is named as AC carbonate which occurs in the crystal lattices of surface soils with invariant content not effected external conditions.In view of its generative relation to hydrocarbons,positive abnormal geochemical haloes formed at surface could be used as indication of oil/gas pool in the underlying strata.The analytical method of AC is studied systematically in this paper.AC analytic device is designed and the analytical procedures of AC carbonates are established after various conditions have been tested.Furthermorer,the method is applied to petroleum exploration of various areas in combination with geochemical researches in order to test the feasibility of the method.