Abstract: Micro-element cathodoluminescence and in situ elemental analysis were used to determine the trace and rare earth elements in calcite samples from the Middle and Lower Ordovician in the northern Shuntuoguole area of the Tarim Basin. The content of rare earth elements in calcite particles was not high, ranging from 0.735 to 24.538 μg/g, with an average of 4.963 μg/g. An obvious enrichment of light rare earth elements and a relative depletion of heavy rare earth elements was observed, with an obvious differentiation between them. There was a slight positive Ce anomaly and an obvious positive Eu anomaly. The Sc, Th contents and the Fe/Mn values were low, while the U/Th and Sr/Ba values were high, indicating that the calcites were deposited in a dry and reducing environment. The comparative geochemical analyses of different occurrences and different periods of calcites and surrounding rock particles were carried out. It is clear that the reservoir geological fluids in the study area mainly came from the formation water of seawater nature, and there were mixed sources of atmospheric water and silicon-rich hydrothermal fluids. It was confirmed that rare earth elements in the original sedimentary wall rocks were relatively rich, and the rare earth elements in calcite grains inherit from the surrounding rocks nearby, but were controlled by the strength of diagenetic fluid transformation.