Physical-layer network coding(PNC) promises substantial theoretical gain to achieve the maximum system throughput in cooperative relay transmission. However, with the increasing global warming, how to reduce power consumption while satisfy system throughput requirement is becoming a vital issue. In this paper, we investigate energy-efficiency resource allocation(RA) based on PNC with amplify-and-forward(AF) protocol in orthogonal frequency division multiple(OFDM) bidirectional transmission. To minimize the overall transmit power consumption with required system throughput requirement, we consider joint subcarriers and power allocation and formulate the objective task into a constrained optimization problem where the best relay node is selected to minimize total transmit power. The closed form optimization power allocation solutions are acquired by analytical derivation. Based on derivation, we propose a novel optimal energy-efficient power allocation(OE-PA). Numerical results are given to evaluate the performance of the derived scheme as compared to other schemes and show that our scheme has signifi cant improvement to energy saving. However, with the increasing global warming, how to reduce power consumption yet satisfy system throughput requirement is becoming a vital issue. In this paper , we investigate energy-efficiency resource allocation (RA) based on PNC with amplify-and-forward (AF) protocol in orthogonal frequency division multiple (OFDM) bidirectional transmission. To minimize the overall transmit power consumption with required system throughput requirement, we consider based on the derivation, we propose a novel optimal energy-efficient power allocation (OE-PA). Numerical results are given to evaluate the performance of the derived scheme as compared to other schemes and show that our scheme has signifi cant improvement to energy saving.