The invention discloses a method for remediating cadmium-contaminated farmland soil by utilizing rape-middle-season rice rotation. The method comprises the following steps: in a first year, soil preparation is performed on the cadmium-contaminated farmland soil to be remediated, an activated base fertilizer is applied to the soil, and Cd-hyperaccumulation rape seeds are sown in a broadcast sowing manner; a foliar activator is sprayed to rapes in the bolting and flowering stages of the rapes; in a second year, the rapes are harvested; after the rapes are harvested, a passivation conditioning agent is applied into the soil, harrowing and waterflooding are performed uniformly, cadmium low-accumulation middle-season rice seeds are directly sown into the cadmium-contaminated farmland soil, and cultivation management is performed; in the tillering, booting and grain-filling stages of middle-season rice, a foliar inhibitor is sprayed to the middle-season rice; and after the rice is ripened, the middle-season rice is harvested. The method provided by the invention adopts the Cd-hyperaccumulation rape and cadmium low-accumulation middle-season rice rotation system, the system cooperates with the activated base fertilizer, the foliar activator, the passivation conditioning agent and the foliar inhibitor, so that the absorption of cadmium in the soil to be remediated by the rapes and the rice is significantly improved, and the remediation effect on the cadmium-contaminated farmland soil is further improved.