Water and sediment samples from surface runoff in the coal mine areas of Guizhou Province were collected and analyzed to investigate pollutant migration from gangues and its impacts on water quality of rivers. Results showed that the pH value of runoff was 2.64～6.38 and the main pollutants in runoff were SO₂^4-,Fe,and Mn. Their concentrations were affected by gangue type and rainfall intensity. After runoff sediment was immersed for 3～28 days,the pH value of upper water reached 2.78~3.71 and the contents of SO₄^2-,Fe,and Mn reached 27～160,0.3～3.9,0.6～2.8 mg/L,respectively. The impacts of surface runoff on water quality of rivers were the acidification of water bodies and serious pollution of Fe and Mn.