Abstract: Error propagation seriously degenerate the diversity order of wireless network coding (NC) system. To address this problem, a novel link adaptive smart NC algorithm is proposed at relay based on log likelihood ratio (LLR). The metric of LLR is employed to replace the statistical characteristics of background noise firstly, so as to promote channel adaption accuracy. Under the virtual source-relay-destination channel model, the posteriori conditional bit error probability is calculated according to the LLR of the received signals. Based on it, the equivalent signal-noise ratio is employed to operate dynamic power scaling by relay. It is theoretically proved that the full diversity order can be attained by this scheme. Simulation results show that the proposed algorithm can maintain full diversity order by mitigating error propagation effectively, and outperform the conventional one.