Abstract: Based on study of relationship between petroleum geochemistry and hydrocarbon migration of the Ordovician oil in Tahe oilfield of the Tarim basin,it was indicated that:a)the physical properties of oil and gas may macroscopically show direction of hydrocarbon migration;b)light hydrocarbon,biomarker and nitrogenous compounds of crude oil can better reflect direction of oil gas migration,i.e.biomark compound of saturated hydrocarbon represents migration direction of relative light oil and nitrogenous compounds are indicator of relative early migration;c)direction of hydrocarbon migration was from south to north in the early stage but it migrated both from south to north and from east to west in the late in Tahe oilfield.