The Xiaoquan-Xinchang Gas Field in west Sichuan and the Houwujiahu Gas Field in south Songliao Basin were selected as the study areas, and core samples from 14 wells were analyzed for such indices as heating released hydrocarbon, acid extracted hydrocarbon and fluorescence so as to study vertical hydrocarbon micromigration. Being influenced by the physical properties of rocks, heating-released hydrocarbon and fluorescence indices show positive gradient in varying degrees. Acid extracted hydrocarbon concentration, however, shows negative gradient in some sectors of oil and gas wells or is not correlative with other geochemical indices. Based on these results, the authors established the hydrocarbon microseepage model and made dynamic simulation. The results of simulation coincide with the measured data.