A method for adjusting parameters of a sending device and a receiving device, and a terminal device are provided. In the method, a new precoding parameter that needs to be used by a sending device on a line when a precoding matrix in a downlink direction of the line changes, and a new signal recovery parameter that needs to be used by a receiving device and matches the new precoding parameter are first acquired; and then the new precoding parameter, the new signal recovery parameter, and a set moment and/or symbol at which the sending device starts to use the new precoding parameter are sent to the sending device, and the new signal recovery parameter and the set moment and/or symbol are sent to the receiving device by using the sending device.