This paper discussed the direction of secondary migration of oil in the No. 6 area of the Melut Basin by making use of nitrogen compounds as secondary oil migration tracers. From the results, we have found that the occurrence and compositional characteristics of isomeric-nitrogen compounds in crude oil precisely manifest the fractionation effect of oil migration: with increasing secondary migration distance, the absolute concentrations tend to decrease, and the ratio of nitrogen-shielded isomers to nitrogenexposed isomers tends to increase. It is considered that the main direction of oil migration in the No. 6 area of the Melut Basin is from north to south.