A smoke detector comprising a body, having a detection chamber therein; a first transmitting tube and a second transmitting tube, arranged in the body and configured to be capable of transmitting a first ray of light and a second ray of light into the detection chamber, respectively; a receiving tube, where the first ray of light and the second ray of light can be incident after refraction and/or scattering, and which generates outputs according to the intensity of incident light; and a control device, coupled with the receiving tube to receive a first output generated by the first ray of light on the receiving tube and a second output generated by the second ray of light on the receiving tube, and configured to determine whether there is a fire based on a difference or ratio between the first output and the second output, or the combination thereof.