Three new genera with three new species and two new species of two known genera, all in the family of Xyelotomidae (Hymenoptera), are described and illustrated. These specimens were collected from the Middle Jurassic of Daohugou, Jiulongshan Formation, and the Late Jurassic to Early Cretaceous of Dawangzhangzi, Yixian Formation, of China. A key to the known and new genera of Xyelotomidae is provided. Fourteen fossil genera with 20 species found so far from the Early Jurassic to the Early Cretaceous imply that Xyelotomidae was diverse and abundant during that period. New findings reported here provide additional evolutionary and transitional evidence of forewing Sc vein changed from two-branched to one-branched, to two separate parts, to apical part forming a crossvein, and finally to vestigial in Xyelotomidae from the Early Jurassic to the Early Cretaceous.