Nowadays LiFePO4 cathode develops rapidly for its advantages of long life span, low cost and non-toxicity, especially in electrical vehicle markets. Because of its stable olivine structure, LiFePO4 is difficult to be recycled by the conventional hydrometallurgical processes as for LiCoO2 or LiNixCoyMnzO2. Pyrometallurgical processes consume much energy and release toxic gases. Herein, an effective room-temperature process based on the mechanochemical treatment is proposed to extract metals from LiFePO4. Spent LiFePO4 is co-grinded with low-cost citric acid agent in a ball mill. After grinding, the mixture is dissolved in deionized water and filtrated. With addition of H2O2, the extraction efficiency of Li reaches as high as 99.35%. Conversely, Fe is hardly extracted with a low extraction efficiency of only 3.86%, indicating a selective recovery of valuable Li element. In addition, when H2O is used instead of H2O2, the mechanochemical reaction changes and the extraction efficiencies of Li and Fe at optimal conditions reach 97.82% and 95.62%, respectively. The Fe impurity is removed as Fe(OH)3 precipitation by adding NaOH, and Li is recycled as Li2CO3 after reaction with saturated Na2CO3 at 95 °C. This simple and easily-operated process has little negative impact on the environment and has great potential in industrial applications.