Abstract: Knowing the pH and Eh values of stream water flowing through the rare earth element deposits can lead to an understanding of the acidity and alkalinity and oxidation-reduction environment of deposits. For this purpose, the Lianshui, Taojiang and Dongjiang rivers in south Jiangxi were selected for study. The dissolved rare earth elements (DREEs) and pH-Eh values of water samples were analyzed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and Three-channel Multi-parameter, respectively. Conclusions are listed as follows: (1) DREEs contents range widely from several μg/L to tens of mg/L, and chondrite-normalized DREEs patterns show a slightly right-inclined trend with Eu and Ce negative anomalies. (2) The weakly negative correlations of DREEs and La contents with pH values indicate that the DREEs contents in water and distribution patterns are affected by the pH values of external environment. (3) Stream water samples flowing through stratums and ion-adsorbed type REE deposits in stratums have pH values of 7.40 and 6.94, respectively, and Eh values of -0.023 V and 6.55 mV, respectively, whereas stream water flowing through granite plutons or weathering crust ion-adsorbed type REE deposits have respective pH values of 6.61 and 4.37, and respective Eh values of 0.024 V and 0.15 V. It indicates that ion-adsorbed type REE deposits formed in a neutral-acid or acid oxidized environment.