Abstract: Bei'er depression is one of the best gas reservoirs in Hailar basin,whose structure styles are mainly faulted block,partly fold structure.The research of fold structure not only finds out fold trap,but analysises structural evolution of basin.Hydrocarbon enrichment in fold structure in Bei'er depression are evidently different.Through the original analysis of fold structure,the author provides that the most favorite fold structure accumulating hydrocarbon is fault nose structure sheltered from the different trend fault and slip anticline structure,and it is worthy for us to continue to research the latter.