Abstract: Important breakthroughs have been achieved in hydrocarbon exploration recently in the Eastern Yangjiang Sag of the Pearl River Mouth Basin. In order to clarify the provenance of sediments and the process of provenance transition of the Eocene Wenchang-Enping Formation in the Eastern Yangjiang Sag, the detrital zircon morphology and ages of 7 sandstones from the Wenchang Formation and the Enping Formation are analyzed, with zircon U-Pb dating method. The results show that: (1) the sediments of the Wenchang Formation are sourced from some peripheral uplifts consisting of Mesozoic magmatic rocks. They are called in-basin provenances in this paper, which, with limited input, is beneficial to the formation of semi-deep lacustrine source rocks. The sediment source as such founded the material basis for petroleum generation in this area. (2) During the time of Early Enping Period, the provenance of the sag is dominated by Caledonian magmatic rocks or their recycled sediments exposed in the area far to the west of the Yangjiang-Yitong Fault Zone. Even the sediments for some small areas are still supplied by the peripheral uplifts, the basin provenances had changed from near-source to far-source ones. While the upper member of the Enping Formation was deposited, the sag is filled by the materials from both South China plate and peripheral uplifts with the gradually increase of material supply from the South China Plate. Both the enhancement of material supply and the weakening of sag-controlling faults lead to the sag dominated by shallow braided delta during the whole Period of Enping Formation.