Pyrite and its weathered products, sampled from the tailings of the Jiguanshan pyrite mine in Tongling, Anhui, have been studied for their mineral composition, texture characters and element distribution. During the weathering of pyrite were formed four fabric types: transitional zone, reticulated ferric oxide, nubby ferric oxide and cellular ferric oxide, which represent the sequence of weathering. The pH value of the pore water plays an important role on the geochemical behaviours of heavy metals, especially Pb and Mn. S was weathered to form sulphuric acid and sulphate, which infiltrated into the pore water. With the progress of weathering, the acidity of the pore water and its solubility of heavy metals gradually increased. The seepage of the fluids exerts a substantial threat on the ecological environment. The changes in element content, enrichment coefficient and leaching coefficient during the weathering suggest that As, Sb, Cu and Zn are obviously concentrated in an ox-idative phase, that Co, Ni and Bi have migrated into water and soils, and that Fe is relatively stable. We thereby conclude: (1) As, Sb, Cu and Zn have formed a potential threat on the environment, in which the harm of As, Cu and Zn is greater than Sb; (2) Co, Ni and Bi have resulted in environmental contamination, in which Bi is more serious than Co, Ni.