A drainage control method for multi-drum washing machine, the multi-drum washing machine comprises at least two washing devices and a drainage pump communicating with the outside. Between each washing device and the drainage pump is respectively provided with a drainage valve. Each washing device of the multi-drum washing machine drains water sequentially. When a washing device completes the drainage, first, the drainage valve of the washing machine is closed, and then the drainage pump is turned off. It is detected whether or not other washing device requires drainage, and if yes, first the drainage valve of the washing device requiring drainage is opened, and then the drainage pump is turned on for the washing device draining water, and if no, the drainage of the multi-drum washing machine ends. The disclosure controls sequential drainage of each washing device, reducing vibration of a washing machine in the drainage process. Moreover, by controlling and determining an operating time sequence of a drainage pump, the disclosure thoroughly drains water in a multi-drum washing machine, extending washing machine service life. The disclosure has a simple structure, low costs, and is suitable for production and promotion.