Abstract: Crop plants irrigated with waste water contained low concentration (under 1mg/l) of arsenic may normally grow and develop, and the arsenic contents accumulated in soils and crop plants are similar to those irrigated with clean water. As the concentration of arsenic rises up to 5 and 20 mg/l, however, the yields of wheat and rice are decreased respectively. Arsenic accumulation in rice increases evidently with irrigated concentration 5 mg/1 of arsenic. It is suggested that approximately 5 mg/l of arsenic may be the critical concentration for the crop plants irrigated with the waste water. A certaim amount of FeSO4 added to the soil may reduce the uptake of arsenic by rice.