【Aim】 Pteromalus sanjiangyuanicus Yang has been identified by morphology as a new parasitic wasp species of the pupal stage of the Gynaephora qinghaiensis. The aim was to further identify P. sanjiangyuanicus at the molecular marker level and explore its phylogenetic relationships within Chalcidoidea, 【Method】 In this study, we sequenced and analyzed the mitochondrial COⅠ gene of P. sanjiangyuanicus and constructed a phylogenetic N-J tree by the neighbor-joining method. 【Result】 The length of the mitochondrial COⅠ gene of P. sanjiangyuanicus was 812 bp after correction, and the contents of A, T, C and G bases were 34.36%, 42.61%, 10.59% and 12.44%, respectively. The content of AT was significantly higher than that of GC, showing obvious AT bias. The COⅠ gene similarity between P. sanjiangyuanicus and Pteromalus puparum was the highest, and the genetic distance was the smallest, indicating that P. sanjiangyuanicus and Pteromalus puparum are closely related. Therefore, it was concluded that P. sanjiangyuanicus may belong to the family Pteromalidae. P. sanjiangyuanicus clustered with Eupelmus sp., Sycoscapter sp., Idiomacromerus sp., Diaziella bizarrea, and Eurytoma sp. and formed a sister group with Idiomacromerus sp. + (Diaziella bizarrea + Eurytoma sp.) + (Eupelmus sp. + Sycoscapter sp.). 【Conclusion】 In this study, analysis at the molecular marker level revealed the close genetic relationships between P. sanjiangyuanicus and Pteromalidae species, which supported the morphological species identification results of P. sanjiangyuanicus and provided a scientific basis for further research on the phylogeny of P. sanjiangyuanicus, which will be of great significance for the biological control of G. qinghaiensis.