Abstract: Vertical hydrocarbon micromigration (caprock and above) resulting in near-surface hydrocarbon anomalies is the theoretical basis and applied premise of geochemical hydrocarbon exploration. The objective exi-stence of vertical hydrocarbon micromigration showed that surface geochemical exploration anomalies were like "a river with sources". The differences of micromigration in the different parts of oil and gas pools revealed the effectiveness of geochemical hydrocarbon exploration. Based on teh geochemical fruits of surface and drilled wells and according to the positive migration gradient of various indexes,the correlation of halo sources and the structural gradient that hydrocarbon is getting lighter upwards,which is widespread in oil and gas wells,the objective existence of vertical hydrocarbon micromigration was revealed,the importance of microfracture network systems was emphasized,the mechanism of micromigration was discussed,and the genetic mechanism of surface geochemical exploration anomalies was well interpreted in this paper.