The invention discloses application of grain amaranth in repairing mine soil and sludge polluted by heavy metal cadmium, wherein the grain amaranth only needs to be planted in the mine soil or the sludge polluted by heavy metal cadmium. By using the characteristic that the grain amaranth enriches the heavy metal cadmium, the grain amaranth is planted in the mine soil or the sludge to be capable ofabsorbing the accumulated heavy metal cadmium and transmitting the most of the heavy metal cadmium to overground part to achieve the aim of repairing the mine soil and the sludge which are polluted by the heavy metal cadmium. The grain amaranth does not need special management in the process of growing, therefore, the invention has the characteristics of less investment, low cost, strong operability, less disturbance to soil environment, permanent managing effect, not breaking site structure, not causing secondary pollution, wide application area, simple post processing, and the like; and thegrain amaranth has large individual biomass, can improve the effect for repairing the heavy metal in unit area, and provides a new plant resource variety for repairing the soil polluted by the heavymetal cadmium.