The invention discloses a method for detecting lithium extraction of a negative electrode of a lithium ion battery. The method comprises the steps of 1, disassembling a to-be-detected lithium ion battery, taking out a negative electrode slice, and clearly cleaning the negative electrode slice by using an organic solvent; 2, soaking the negative electrode slice in an organic solution of metal salt Mn<+>, enabling Mn<+> and extracted lithium to be subjected to sufficient replacement reaction, taking out the negative electrode slice after the replacement reaction is completed, and then cleaning the negative electrode slice by using the organic solvent to obtain the clean negative electrode slice; 3, carrying out qualitative or quantitative analysis on a product M through an energy spectrum analyzer, X-ray diffraction, an X-ray fluorescence spectrum, or an X-ray photoelectron spectroscopy, an atomic absorption spectrum or an inductive coupling high-frequency plasma by the negative electrode slice after the replacement reaction, and further determining whether the negative electrode is in the lithium extraction or not and the relative size of the lithium extraction amount. According to the method disclosed by the invention, whether the negative electrode of the lithium ion battery has the lithium extraction or not can be accurately detected, so that the situation that the safety of the lithium ion battery is affected due to the lithium extraction of the negative electrode can be avoided, the service life of the lithium ion battery is prolonged, the safety of the lithium ion battery is increased, the operation is simple and convenient, and the detection accuracy is higher.