According to the characteristics of rock particle composition, the sandstone reservoir of the Xujiahe Member 4 of Upper Triassic in western Sichuan Depression can be divided into three categories: feldspar lithic sandstone, lithic quartz sandstone and lithic sandstone, of which the quality of feldspathic lithic sandstone reservoir is the best. By means of cast thin section observation, cathodoluminescence and electron microprobe analysis, it is considered that carbonate cement is an important factor affecting reservoir quality and continuous calcite and calcite cement with grain structure play a very important role in affecting reservoir quality. The enrichment law and trace element content change of carbonate cements are analyzed. It is found that different types of sandstone develop crystal stock calcite, crystalline calcite and dolomite cements, and the characteristics of cement content, cathodoluminescence and trace element composition reflect the differences of their sources. The cathodoluminescence of crystal stock calcite is bright yellow, with high Fe2+, Mn2+ contents, and low Sr2+ content. It has the characteristics of trace element composition caused by atmospheric fresh water, which confirms that it is affected by the leaching of atmospheric fresh water. Microcrystalline, very fine crystalline, fine crystalline and medium crystalline calcite has the cathodoluminescence of orange red to orange yellow, and the calcite filling in feldspar dissolved pore has the cathodoluminescence of dark and bright for multiple generations, reflecting the variation of Fe/Mn value from high to low. The middle crystalline calcite and calcite filling in feldspar dissolved pore are characterized by high Fe2+, Mn2+ contents and low Mg2+ content. It is considered that because feldspar and clay minerals are affected by organic acid dissolution during burial diagenesis, the resulting high Fe2+ and Mn2+ concentrations in diagenetic system, and the high distribution coefficient of Mn2+ and Fe2+ in the diagenetic process of carbonate cement determine the distribution characteristics of trace element in the cements. Therefore, ions forming crystalline carbonate cement mainly comes from the dissolution of feldspar and clay minerals during burial.