The present invention relates to a cell phone guarding method basing on the optical inductor of the cell phone applies the change of light-sensing intensity of the optical inductor which is arranged in the cell phone to automatically trigger the alarm, preventing the cell phone being stealing or losing. The specific method includes the steps that a steal-proof software module is arranged in the cell phone provided with an optical inductor, and then a keysoke or keystoke assembly which is preinstalled is pressed to make the cell phone with the condtion of steal-proof mode; during the period which is preset before the alarm device is started, the cell phone has to be put into the handbag or other place insulated from the light; when the preset period is out, the steal-proof software module drives the cell phone to open the optical inductor. If the light intensity is dim or no light, the cell phone does not alarm; or, once the cell phone is taken out from the handbag or fallen out accidently, the light intensity of the optical inductor is stronger than the set value, the alarm is promptly triggered, informing that the cell phone is probably stolen. The method of the invention is low in cost, convenient in usage and wide in applicability, being applicable in variable cell phones which are provided with the optical inductors.