Abstract: This paper investigates the strategy of relaying based on opportunistic network coding over wireless communication context with two pairs of users and one common relay exchanging their data, where the relay node can transmit either network-coded or un-coded packets, and presents that this strategy of relaying can substantially decrease the system power consumption against the traditional strategy of copy and forward. Although the traditional strategy can almost surely induce the delay for packets, the strategy of relaying based on opportunistic network coding can also bring in the same result if the relay node pursues just only the energy efficiency. Resorting to a Markov model, the paper characterizes the average delay and power consumption for each packet when using the relaying strategy based on opportunistic network coding. The results of simulation indicate that there exists some tradeo? between delay and power consumption. For the case of bu?er size M = 1, the tradeo? is presented.