A light sensor and control method thereof, which controls the light sensor comprising a first light emitted element, a second light emitted element, a first light sensing element and a control circuit. The light wavelength of the second light emitted element is greater than the light wavelength of the first light emitted element. The control circuit is coupled to the first and second light elements and the first light sensing element. When the display of an electronic device is in a light-up status, the control circuit switches on the first light emitted element to emit light; when the display of the electronic device is in a light-off status, the control circuit switches on the second light emitted element to emit light. Thus, it will prevent from the influence to the image of the display, and obtained the better sensing ability.