The discovery of basement reservoir in Kunbei fault terrace belt is an important exploring breakthrough in southwestern Qaidam Basin. Based on the analysis of well logging data, core observation, section identification and imaging well logging data, the lithology, reservoir space and influencing factors of basement reservoir in Kunbei fault terrace belt are expounded. The result shows that the lithologies are mainly granite and slate, the reservoir spaces contain tectonic fissure, dissolved fissure and dissolved pore, and the reservoir type is fracture-dissolution. The analysis of physical property and thin section illustrates that basement reservoir has low permeability and complex reservoir space, but the dissolved pore along the fracture has good physical property. Finally, the main factors such as the lithology of basement rock, tectonic movement and diagenesis which influence the development of reservoir space are analyzed.