A method, a device and a system for precoding based on CoMP are provided. The method includes: a serving base station receives an expected PMI of a terminal associated with the serving base station and a leakage PMI of a terminal associated with a cooperation base station, which is sent by the cooperation base station, wherein the expected PMI is corresponding to encoding codeword in an expected terminal direction, and the leakage PMI is corresponding to encoding codeword in an interference direction; the serving base station selects expected encoding codeword according to the expected PMI and selecting leakage precoding codeword according to the leakage PMI; and the serving base station convolve the expected encoding codeword and the leakage precoding codeword to obtain precoding codeword used for signal transmission by the serving base station. In the present invention, by use of the CoMP technology, the accuracy of reducing interference of edge user terminals is improved.