Abstract: Lower Silurian sandstone of the Xiaoheba formation in Southeastern Sichuan has a good reservoir seal combination, and an oil and gas geological condition, but the hypothesis that the sedimentary environment belongs to continental or marine sedimentary deltas remains a matter of debate. In order to solve this problem, 74 samples were collected from 9 typical sections. The elemental composition was determined by the trace element ratio method. Combined with the tectonic background and source characteristics, the sedimentary and paleoclimatic environment were discussed. X-ray Fluorescence Spectrometry (XRF) was used to analyze Ba, Mn, Sr, Cu and other trace elements, which are useful in discriminating between the sea and land facies sedimentary environment. The results show that the average Sr/Ba value is 0.2790 with the maximum of 2.31, the Mn/Fe value is 0.0093 to 0.0778, and the Sr/Ca value is 0.0005 to 0.0414, typical of freshwater delta sedimentary characteristics. The average Sr/Ba is less than 1, the average Sr/Cu is 4.8758, and more than 8.1% samples have Sr/Cu values greater than 10, reflecting the warm, moist, ancient climate environment.