The disclosure relates to a draining structure of a washing machine and a draining method. An inner drum is installed in a housing of the washing machine. The inner drum is a tapered drum with a smaller diameter at one end and a larger diameter at the other end. A draining flow passage is arranged at the larger diameter end. One end of the draining flow passage communicates with the larger diameter end. The other end of the draining flow passage penetrates the inner drum and communicates with a drain pipe. The inner drum rotates and washing water flows to the larger diameter end along the tapered inner wall by centrifugal force. Washing water is drained out from the inner drum through the draining flow passage arranged at the larger diameter end and then drained out through the drain pipe to realize the discharge of washing water.