A method of lithium ion battery in-situ detection is proposed. In the proposed method, gold-plated fiber Bragg grating(FBG)sensors are embedded in the making process of lithium ion batteries to acquire the initial physical quantities of lithium ion batteries. The position and the method for the FBG sensor embedded in lithium ion battery are studied, and the performance of battery embedded with gold-plated FBG sensor is analyzed. The charge-discharge experiments for lithium ion batteries are carried out, and the battery samples used in experiments are unpacked. The experimental results show that gold-plated FBG sensors can be used in the temperature collection in general environment. The gold-plated layer structure in the lithium ion battery is corroded, which results in wavelength drift. The bare FBG′s structure is not destroyed due to the presence of the gold-plated layer, so the internal temperature of battery can be collected after re-calibrating FBG sensor. This research provides a reference for the FBG sensor used in in-situ detection for lithium ion batteries.