A transmitter for a multi-user multiple-input multiple-output, MU MIMO system, wherein the MU MIMO system comprises the transmitter that communicates with at least two receivers, and the transmitter comprises: a determining unit that is configured to, for each receiver of the at least two receivers: determine a transmitting precoding vector of a primary pilot signal of the receiver according to first spatial channel information, and determine an estimated receiving filtering vector according to the transmitting precoding vector of the primary pilot signal and second spatial channel information; determine a transmitting precoding vector of a secondary pilot signal of the receiver according to the estimated receiving filtering vector and the first spatial channel information; and determine a to-be-sent primary pilot signal of the receiver according to the transmitting precoding vector of the primary pilot signal and a preset initial primary pilot signal, determine to-be-sent user data of the receiver according to the transmitting precoding vector of the primary pilot signal and preset user data of the receiver, and determine a to-be-sent secondary pilot signal of the receiver according to the transmitting precoding vector of the secondary pilot signal and a preset initial secondary pilot signal, wherein the first spatial channel information is information about spatial channels between the transmitter and the at least two receivers, and the second spatial channel information is information about a spatial channel between the transmitter and the receiver; and a sending unit, configured to, for each of the at least two receivers: send to the receiver the to-be-sent primary pilot signal of the receiver, the to-be-sent user data of the receiver, and the to-be-sent secondary pilot signal of the receiver that are determined by the determining unit; wherein the primary pilot signal and the secondary pilot signal are orthogonal to each other; characterised in that the transmitting precoding vector of the secondary pilot signal of the receiver is orthogonal to a third spatial channel, wherein the third spatial channel is a spatial channel between the transmitter and all other receivers in the at least two receivers other than the receiver. determine a transmitting precoding vector of a primary pilot signal of the receiver according to first spatial channel information, and determine an estimated receiving filtering vector according to the transmitting precoding vector of the primary pilot signal and second spatial channel information; determine a transmitting precoding vector of a secondary pilot signal of the receiver according to the estimated receiving filtering vector and the first spatial channel information; and determine a to-be-sent primary pilot signal of the receiver according to the transmitting precoding vector of the primary pilot signal and a preset initial primary pilot signal, determine to-be-sent user data of the receiver according to the transmitting precoding vector of the primary pilot signal and preset user data of the receiver, and determine a to-be-sent secondary pilot signal of the receiver according to the transmitting precoding vector of the secondary pilot signal and a preset initial secondary pilot signal, wherein the first spatial channel information is information about spatial channels between the transmitter and the at least two receivers, and the second spatial channel information is information about a spatial channel between the transmitter and the receiver; and a sending unit, configured to, for each of the at least two receivers: send to the receiver the to-be-sent primary pilot signal of the receiver, the to-be-sent user data of the receiver, and the to-be-sent secondary pilot signal of the receiver that are determined by the determining unit; wherein the primary pilot signal and the secondary pilot signal are orthogonal to each other; characterised in that the transmitting precoding vector of the secondary pilot signal of the receiver is orthogonal to a third spatial channel, wherein the third spatial channel is a spatial channel between the transmitter and all other receivers in the at least two receivers other than the receiver. send to the receiver the to-be-sent primary pilot signal of the receiver, the to-be-sent user data of the receiver, and the to-be-sent secondary pilot signal of the receiver that are determined by the determining unit; wherein the primary pilot signal and the secondary pilot signal are orthogonal to each other; characterised in that the transmitting precoding vector of the secondary pilot signal of the receiver is orthogonal to a third spatial channel, wherein the third spatial channel is a spatial channel between the transmitter and all other receivers in the at least two receivers other than the receiver.