The invention discloses a method for reducing the content of cadmium in rice. The method includes the steps that in farmland polluted by cadmium, tobaccos are planted in the first half year, and rice is planted in the second half year. A rice planting method includes the following steps that 1, biochar and a soil heavy metal passivant are mixed and scattered on the surface of soil of the farmland polluted by cadmium, then the biochar, the passivant and the soil are mixed to be even, after three days, a base fertilizer is applied, and rice is transplanted, wherein the amount of the adopted biochar is 50-150 kg / hm<2>, and the quantity of the adopted soil heavy metal passivant is 300-6,000 kg / hm<2>; 2, when the rice grows to be in the booting stage, water-solubility leaf silicon fertilizers are sprayed twice, wherein the spraying time interval of the water-solubility leaf silicon fertilizers is 5-7 days, and the quantity of the adopted water-solubility leaf silicon fertilizers is 1,500-6,000 ml / hm<2>. According to the method, the content of cadmium in rice is reduced through the combined effect of the biochar, the soil heavy metal passivant and the water-solubility leaf silicon fertilizers; the biochar serves as an effective component for reducing the content of cadmium in rice, raw materials of the biochar are easy to obtain, and cost is low; the content of cadmium in rice is further reduced through the biochar prepared from tobacco straw and waterflooding management.