REE fractionation during the weathering of dolomite has been recognized for decades. A regolith profile on dolomite in southwest Yunnan of China was selected to investigate the behaviors of REE during weathering. The weathering of dolomite is divided into two stages: the pedogenesis stage and soil evolution stage, corresponding to the saprolites and soils respectively in the regolith profile. SiO2, TiO2, P2O5, Zr, Hf, Nb and Ta were immobile components during the weathering by and large, while Al2O3, K2O and Fe2O3 were lost during the soil evolution stage in the physical form (clay minerals probably). REE were fractionated during the whole weathering of dolomite. The field weathering profile and the lab acid-leaching experiments on dolomite indicate that MREE were enriched clearly relative to other REE during the pedogenesis stage in a “capillary ascending-adsorption” mechanism, but they did not fractionate clearly in the soil evolution stage. REE were lost and accumulated in the weathering front of dolomite during the soil evolution stage in a “physical-chemical leaching” mechanism.