Abstract: Embodiments of the present invention provide a downlink precoding method and data interacting method for coordinated multi-point transmission system and apparatus. The downlink precoding method includes: acquiring a precoding matrix indicator by a cooperating point and determining the precoding matrix of the cooperating point according to the precoding matrix indicator, the number of columns of the precoding matrix of the cooperating point being less than that of columns of the precoding matrix of a serving point; and performing, by the cooperating point, downlink precoding to the data to be transmitted according to the determined precoding matrix of the cooperating point. With the methods and apparatuses of the embodiments of the present invention, as the cooperating points participate only in the transmission of data of part of layers in the coordinated scenarios, the complexity of calculation and the feedback overhead are lowered in the UE end.