A new genus and three new species of fossil Palaeontinidae, Papilioncossus conchatus sp. nov., P. giganteus sp. nov.and P. pteroideus sp. nov., are described. All of them were collected from Middle Jurassic Jiulongshan Formation in Inner Mongolia,China. Based on distal part of forewing broader and longer than basal and Sc usually with branches, the new taxa are attributed to Palaeontinidae of Homoptera and compared with genus Pseudocossus. A key to species of Papilioncossus gen. nov. is provided. All type specimens are deposited in the Capital Normal University.