The invention discloses a nondestructive testing method for lithium precipitation of a lithium ion battery. The method comprises the following steps: S1, charging a flexible package lithium ion battery to be tested to a set state, and standing; S2, in a charging process and a standing process, collecting a thickness of the flexible package lithium ion battery to be tested in real time, and drawinga thickness curve graph of the thickness changing with time; and S3, if the thickness curve graph shows that the thickness is firstly reduced along with time and then is kept stable, judging that theflexible package lithium ion battery to be tested has a lithium precipitation phenomenon. In the invention, whether lithium precipitation occurs in the lithium ion battery can be analyzed in a nondestructive manner only according to the acquired thickness curve of the flexible package lithium ion battery, operation is simple, easy to understand, convenient and rapid, judgment accuracy is improved, a user does not need to disassemble a battery cell in the battery, and safety is improved; and the method can be used as a basis for battery failure analysis in a battery aging process, and also canprovide a basis for optimizing a battery design and a charging method.