XRF elemental analysis is used to determine the ancient depositional environment and sedimentary microfacies of sandstone reservoirs. By analyzing elements like Sr, Mn, Ti, Mg, Ca, and Fe, researchers identified environmental discrimination elements and excluded data from cementing development layers. Normalizing relevant elements and using elemental ratios helped determine the sedimentary environment accurately. This method provides a basis for fine grading of sedimentary microfacies in sandstone reservoirs.