As Information,Communications,and Data Technology(ICDT)are deeply integrated,the research of 6G gradually rises.Meanwhile,feder-ated learning(FL)as a distributed artificial intelli-gence(AI)framework is generally believed to be the most promising solution to achieve“Native AI”in 6G.While the adoption of energy as a metric in AI and wireless networks is emerging,most studies still fo-cused on obtaining high levels of accuracy,with little consideration on new features of future networks and their possible impact on energy consumption.To ad-dress this issue,this article focuses on green concerns in FL over 6G.We first analyze and summarize major energy consumption challenges caused by technical characteristics of FL and the dynamical heterogene-ity of 6G networks,and model the energy consump-tion in FL over 6G from aspects of computation and communication.We classify and summarize the ba-sic ways to reduce energy,and present several feasible green designs for FL-based 6G network architecture from three perspectives.According to the simulation results,we provide a useful guideline to researchers that different schemes should be used to achieve the minimum energy consumption at a reasonable cost of learning accuracy for different network scenarios and service requirements in FL-based 6G network.