The present invention relates to the field of wireless communications technologies, and discloses a method and device for pre-coding and a method and device for decoding. The present invention implements an interference alignment method with excellent performance, can effectively increase the capacity of a multi-user interference system and reduce the mutual interference among users, The method for pre-coding includes: calculating a pre-coding matrix for each transmitting end according to a sum of mean square errors of data vectors to be transmitted by each transmitting ends; and using the pre-coding matrix to pre-code the data to be transmitted by each transmitting end. The present invention has broad application prospects, for example, can be used in LTE and LTE-Advanced CoMP technology.