Abstract: Keluo complex at Nenjiang area in Heilongjiang Province is located in the northern part of the Daxing′anling Mountains. By detailed field work and structural analysis we found that the Keluo complex has developed a large scale detachment structure, including sheath folds, wrinkle in soft layer, asymmetric folds, S-C fabric, elongated lenses, eye-like structure, drag structure and so on, which suggests a top to south-east extensional sliding. Combining with the chronologic and petrological evidences, we think that the extensional deformation of Keluo complex should happen in Late Jurassic in Daxing′anling region, and resulted in the uplift of Daxing′anling Mountains and the regional extensional detachment, and formed the metamorphic core complex. Our research on extensional structure of Keluo complex provides a new evidence for the uplift mechanism study of Daxing′anling Mountains.