The Paleogene saline-facies fracture marlstone is one of the important reservoir types in the western Qaidam Basin. Effective fractures not only provide storage spaces and channels for fluid flow, but also determine enrichment rule and output potential of oil and gas. The fracture validity is controlled mainly by formation time, dissolution, uplift and denudation since the Quaternary, abnormal fluid high pressure, distribution of gypsum and salt beds, and fault activity. Late fractures are more effective than early fractures. Dissolution can obviously increase the fracture validity. Since the Quaternary, tectonic uplift and denudation, and abnormal fluid high pressure make filled fractures reopen, improving the fracture validity. The farther fractures distribute from gypsum and salt beds, the better the validity.