The invention discloses an oxidation-preventing cell light decay device, which comprises a first chamber and a second chamber. The two chambers are divided and sealed by a high light-transmission baffle from the top to the bottom of the shell. The first chamber further comprises a sunlight simulation component disposed in the first chamber; and the second chamber further comprises a door arranged on the side wall of the second chamber in an opening and closing manner. A carrying platform and the high light-transmission baffle are arranged in the second chamber in parallel. A nitrogen charging component is communicated with the second chamber through a conduit. A temperature sensor is arranged on the carrying platform. A speed-adjustable heat-radiating fan is arranged on the side wall of the first chamber; and a temperature controller is in communicative connection with the temperature sensor, and the temperature controller is electrically connected with the speed-adjustable heat radiating fan. The device of the invention can perform temperature-and-time-controllable light decay testing on a cell under the condition that the cell is fully protected from being oxidized or damaged so that the electric performance of the cell decays to a stable state and that the accuracy of secondary cell and testing can be ensured.