The invention discloses a method for discharging tailing sand from the bottom of a movably settling open pit. The method comprises the following steps that S1, a cover layer is arranged; S2, a filter well is constructed; S3, a cemented tailing sand layer is poured; S4, a water filtration pipe network is installed; S5, tailing sand subjected to desliming is discharged; S6, the filter well is filled up; S7, the steps from S3 to S6 are repeated till the open pit is filled up. According to the method for discharging the tailing sand from the bottom of the movably settling open pit, the open pit can be used as a piling bank for transferring in tailings of an underground mine, so that a series of problems concerning mine tailing bank construction are effectively solved, and tailing bank construction and maintenance capital is saved on the premise of guaranteeing underground mining operation safety. An instability disaster of a slope of the open pit is effectively controlled, the underground drainage cost is reduced, good closure of the caving method mining cover layer is ensured, reclamation of the open pit is promoted, the mining cost is greatly reduced, and the environment is protected.