A drainage structure of a washing machine and a drainage method therefor. An inner tub (1) is mounted in a shell of the washing machine; the inner tub (1) is a conical tub with a small diameter at one end and a large diameter at the other end; the large end of the inner tub (1) is provided with a drainage passage (32); one end of the drainage passage (32) is communicated with the large end of the inner tub (1), and the other end thereof penetrates through the inner tub (1) via the center of the large end and is communicated with a drainage pipe (31) of the washing machine. The inner tub (1) rotates at a certain rotating speed, so that washing water in the inner tub (1) flows to the large end along the inner wall of the conical inner tub (1) under the centrifugal force; when flowing to the large end of the inner tub (1), water flows from the center of the large end of the inner tub (1) along the drainage passage (32) provided at the large end, and flows out of the washing machine along the drainage pipe (31) t
