A method for analyzing a swelling behavior of a lithium secondary battery includes: (S1) installing a detachable pressurizing holder for fixing a battery sample and a charge/discharge cable connected with an external charging/discharging device to an X-ray CT (computed tomography) imaging equipment; (S2) inserting the battery sample into the pressurizing holder, contacting an electrode lead of the battery sample with a terminal of the charge/discharge cable, and then operating the external charging/discharging device to perform charging and discharging; and (S3) while rotating the battery sample during charging and discharging of the battery sample, irradiating and scanning the X-ray on the battery sample at an angle ranging from −10° to 10° to obtain a 3D image, and then measuring a change in the thickness of the electrode inside the battery sample from the 3D image.