A method and device for sending service data are provided in the present invention, so as to realize simplification of a precoding matrix calculation method. The method includes: a network side executing the following steps: calculating a value space matrix according to a signal channel matrix of a serving cell of a terminal; calculating a null space matrix according to an interference channel matrix of a coordinating cell of the terminal; projecting a vector of the value space matrix to a space on which a vector of the null space matrix is located to obtain a precoding matrix of the terminal; and sending the service data in the serving cell of the terminal according to the precoding matrix.