The Tonian period marks one of the most critical time intervals in the evolutionary history of the early life and environment. It follows a golden age of cyanobacteria in the Mesoproterozoic and precedes a global biological collapse in the Cryogenian. The southern Jilin Province, situated on the northeastern margin of the North China block, offers an excellent opportunity to study paleontology, biostratigraphy and paleoenvironment during the Tonian period. This region boasts complete sedimentary successions of strata, wellexposed outcrops, and the presence of various wellpreserved microfossils within chert bands, nodules, and shales. In this study, we present an assemblage of microfossils discovered in cherts from the uppermost sediments of the Wanlong Formation in the Erdaojiang area of south Jilin Province. We have identified a total of nine species belonging to six genera, including filamentous cyanobacteria such as Siphonophycus robustum, S. typicum, S. kestron, S. solidum, spheroidal cyanobacteria such as Eoentophysalis belcherensis, Gloeodiniopsis lamellosa, Scissilisphaera bistratosa and incertae sedis species like Glenobotrydion majorinum, Globophycus rugosum. These newly documented microfossils provide valuable insights into the paleoenvironment of the Wanlong Formation and facilitate the regional correlations of biostratigraphy. Furthermore, the microbiota is predominantly composed of cyanobacteria filaments, particularly Siphonophycus mat, with horizontally oriented filaments typically exceeding 400 μm in length, indicating taphonomic characteristics of autochthonous or nearautochthonous preservation. The comprehensive analysis of the paleoenvironment suggests that the uppermost sediments of the Wanlong Formation in the Erdaojiang area of south Jilin Province represent a shallow, low intertidal or subtidal environment with a low sedimentation rate.