The invention discloses a symbol-based physical-layer network coding method for a two-way 
relay communication 
system. The method comprises the following steps that: in a first time slot, during the receiving of information through a 
relay node, two source nodes send respective modulated signals to the 
relay node respectively, and the relay node performs self-correlation operation on the received superposed signals to obtain a self-correlation matrix and detects a network coding symbol to be broadcast from the self-correlation matrix by using a maximum-likelihood (ML) detection 
algorithm to reduce a detection space of the network coding symbol, so the difficulty of 
signal detection is reduced, a receiving 
diversity gain is obtained, and the error code performance of the 
system is guaranteed; and in a second time slot, during the 
broadcasting of the information through the relay node, the relay node broadcasts the detected network coding symbol, and the two source nodes respectively decode the received signals by using a self-
interference elimination method to obtain the information of the opposite-side node, so a communication process is finished. The invention has the advantages that: the operation complexity of a relay 
processing signal is reduced by using the characteristics of an M-ary 
phase shift keying (MPSK) 
signal; the receiving 
diversity gain is obtained; and the method is applicable to an MPSK modulation 
system at symmetric and asymmetric speed rates under a two-way 
relay channel.