Based on a systematic study of sedimentary profile from downstream of the Maoniuping REE deposit, the authors investigated the environmental impact of mine development on fluvial deposits. The results show that the sediment profile can be divided into four stages: 0~10 cm,10~30 cm,30~40 cm and 40~50 cm. The authors determined the depositional age of the sediment profiles by ²¹⁰Pb. The average deposition rate of the river is 0.45 cm/a since 1910. According to the rate of sediment profiles, the deposition can be divided to four stages: The first stage is 1910~1940, whose deposition thickness is about 5 cm and whose average deposition rate is 0.168 cm/a. At this stage the content of K, Na, U, S, Mo, Mn, Pb and F decreased gradually. The second stage is 1940~1990, whose deposition thickness is about 22 cm and whose average deposition rate is 0.44 cm/a. At this stage the shallow 12 cm showed the characteristics of high pH, N, P and organic matter but low K, Na, U, S, Mo, Mn, Pb and F, whereas the deep 10 cm presented the characteristics of high K, Na, U, S, Mo, Mn, Pb and F. The third stage is 1990~1999, whose deposition thickness is about 8 cm and whose average deposition rate is 0.889 cm/a. At this stage there existed the characteristics of high pH, N, P and organic matter but low K, Na, U, S, Mo, Mn, Pb and F. The fourth stage is from 1999 up till now, whose deposition thickness is about 10 cm and whose average deposition rate is 0.909 cm/a. This stage presents the characteristics of low pH, N, P and organic matter but high K, Na, U, S, Mo, Mn, Pb and F.