Abstract: The special sedimentary and tectonic evolution in Gucheng area of the Tarim Basin indicated that dolomite formation might be unique. The REE geochemical characteristics of various kinds of crystalline dolomites and cave fillings were analyzed based on thin sections, cores and sedimentary environment analyses. The results showed that the NASC normalized REE distribution patterns of samples can be divided into four types: negative anomaly δCe and weak positive anomaly δEu, negative anomaly δEu, positive anomaly δEu, and positive anomaly δCe. Further studies showed that the main origin of dolomites was the evaporation pump model, and the hydrothermal environment was also important, while the influence of mixed water and burial dolomitization was relatively smaller. In addition, all the cave filling samples were formed in a mixed water and hydrothermal environment, while the evaporation pump and burial dolomitization did not form any filling samples, which might be helpful to find dolomite reservoirs.