Abstract: The pyrite mine in Yun-fu couaty of Guangdong province has become the largest one in China now. The deveopment of this mine affected a land area of nearly 9 km2 causing serious soil and water losses. At the same time it brought to the surroundings a large number of pollutants which polluted In different degrees the ecological environment of the lower reachs.Such element as Fe,Mn,Pb,As.Cd etc.in the acid Water discharged from the mine Were the major pollutants to the cropland environment. The concentrations of these elements at the outlet of GaO-feng river Were 25.0, 5.52, 0.17, 0.038, and 0.014 ppm respectively,the pH value Was 4.21.The effect of the acid Water on rice growth Was essential in evaluating the influences the mine may made to the cropland ecological environment. Through investigations of the current situation, pot experiments, and earth-pillar and acid Capacity lests, the soil/environmental capacity has been determined. The results of conlprehansive analysis indicated lhat mine development would not cause great effect to the cropland ecological environment if soil and Water loss would be controlled and the land could be kept away from the flooding water. The expenses of waste water treatment which amounts about 2000, 000 yuan per year may be saved if the environmental capacity of soil could be utilized.