In this study, selenium (Se) contents of agricultural soil, soil profile, irrigation water, bedrock, coal fly ash, paddy rice and vegetables in the vicinity of coal fly ash reservoir are determined. Se concentration in agricultural soils surrounding coal fly ash reservoir ranged from 0.15 to 6.12 mg/kg. The topsoil was polluted at different levels. The closer to the coal fly ash reservoir agricultural soils were, the more seriously polluted by Se they were. These results of different Se sources imply that the high Se level in agricultural soils is mainly caused by long-term of coal fly ash deposit and sewage irrigation, rather than by parent material. Se concentration in paddy rice ranged from 0.04 to 1.12 mg/kg and five paddy rice grain samples exceed the food hygiene concentration limit of 0.3 mg/kg. Se concentration in paddy rice was positively correlated with total Se concentration in soil, suggesting that Se in soil was readily transferred into the crops. Therefore, there is a potential health risk from local staple food in the study area.