There maybe exist multiple source supply during the sedimentation period of the Chang 9 oil reservoir set in Longdong area. Provenance analysis is not only the basis of study the delta development characteristics of Chang 9 oil reservoir set, but also the foundation for evaluation and prediction of sand bodies. Based on the relative change of quartz content, heavymineral assemblages, quartz cathodoluminescence, debris content and paleosalinity recovery, it is considered that the deposition is controlled by the sources from the southwest, the northwest, the south and the northeast of Longdong area at the same time. The southwest of the study area is the main source area, followed by the south, the northwest and the northeast. The parent rocks in the southwest are middle-high grade metamorphics and volcanics in the Qilian tectonic belt, while the source in the south, the northwest and northeast is granite and low-middle grade metamorphics fromthe Southern Qinling tectonic belt, Alaschanica ancient land and Yinshan ancient land respective. The sediments that come fromdifferent directions converge at the area ofYuancheng-Huachi-Majiabian-Taibai.