The age of the Dahesen Formation in Huadian County, Jilin Province, is debated for a long time. The majority authors assigned this formation to Early Permian. The present authors systematically collected conodont samples from named-section of this formation, and found some conodonts inclu- ding Mesogondolella aserrata , Mesogondolella da- heshenensis sp. nov. Wang, Mesogondolella sub- gracilis sp. nov. Wang, Mesogondolella sp. B, Mesogondolella sp. X. Based on mainly the pres- ence of Mesogondolella aserrata, the age of the Daheshen Formation should be assigned to Word- ian Stage of Middle Permian.