It is very important to investigate and assess ecological environment quality of mines and neighborhood areas for ecological environment monitoring and protection. In order to assess the potential ecological risk of heavy metals contamination in sediments resulting from past mining activities in Dexing region, 330 Sediment samples in Dexing region were collected and analyzed for As, Hg, Cd, Cr, Zn, Cu and Pb in 2004. Heavy metal levels were determined using inductively couple plasma atomic emission spectrometry and X-ray fluorenscence spectrometry procedures. The contents of sediments samples reported concentrations between 3.070~1 109 mg/kg for As, 0.015~5.430 mg/kg for Hg, 0.035~13.5 mg/kg for Cd, 7~236 mg/kg for Cr, 22~1 770 mg/kg for Zn, 5~4 390 mg/kg for Cu, and 15~1 685 mg/kg for Pb, respectively. Meanwhile, The potential ecological risk was to assess with potential ecological risk was assessed with potential ecological risk coefficient ranged form 2.362~853.077 for As, 2.000~621.000 for Hg, 5.250~2025.00 for Cd, 0.250~8.4290 for Cr, 0.134~10.793 for Zn, 0.588~516.471 for Cu and 2.174~244.203 for Pb respectively. The potential ecological risk index ranged form 27.597~3747.572. Meanwhile, GIS (Geographic Information System) spatial analysis methods were adopted to represent the spatial distribution of heavy metal contamination. The results of the assessment indicated consistently that there were different extents of potential ecological risk of As, Hg, Cd, Cu and Pb, especially in the areas of the Dexing river and Dawu river around Dexing mines, along the lower courses of Le'an river, some coal mines in the northwest.