The aquatic macrophyte Eleocharis acicularis from Cyperaceae family have been reported to be a hyperaccumulator of heavy metals such as As, Fe, Ag, Cd, Cs, Cu, In, Pb, and Zn in laboratories and field experiments. This study aimed to determine heavy metal accumulation in E. acicularis at heavy metal-rich mine drainage and to reveal the plant ability to uptake heavy metals in waste drainage with addition of silicon fertilizer in E. acicularis for phytoremediation. The floating mats of E. acicularis were transplanted in the two of mining wastewater pond in a mining site of Southwest Japan. The result indicates that the bioconcentration factors of Fe, Cu, Zn, As, and Pb shows the E. acicularis is a hyperaccumulator of heavy metals in the water. However, there are no effects on the addition of silicon fertilizer in correlations between silicon concentration and heavy metal in E. acicularis.