Based on geochemical analysis, including the degree of order, carbon and oxygen isotopes, rare earth elements and inclusions, the types and generation mechanism of Cambrian dolostone samples from outcrops at Fandian, Yankong and Sanhuichang in the south of Sichuan Basin are investigated. It is shown that contemporaneous microcrystalline dolomite, fine-crystalline dolomite, shallow-buried fine-crystalline dolomite and saddle dolomite mainly develop in the study area. The microcrystalline dolomite and fine-crystalline dolomite are of low order degree, and similar to δ18O values of the normal marine carbonate rocks in the same period. Their REE distribution pat erns are approximate consistent, which is characterized by weak accumulation of HREE and weak loss of LREE. The dolomitization fluid that mostly originates from high-salinity seawater is considered as the product of the evaporation pump dolomitization and the seepage reflux dolomitization. The order degree for fine-crystalline dolomite is relatively high and the rare earth elements display depletion and migration with decreasing ΣREE values. It is considered as the result of the burial dolomitization. The saddle dolomite is characterized by high order degree, lowδ18O value, enrichment of REE, Eu positive and negative, extremely high homogenization temperature of inclusions and a double range distribution, which indicates that the dolomitization fluid maybe derived deep hydrothermal fluid, or as the product of the hydrothermal dolomitization.