A smoke detector comprising: a first light source, configured to generate first light beam; a second light source, configured to generate second light beam; a light receiver, configured to respectively generate a first and a second original light detecting signal in response to the first light beam and the second light beam, wherein an energy conversion efficiency of the light receiver at the first wavelength is different from an energy conversion efficiency of the light receiver at the second wavelength; a signal adjusting circuit, configured to amplify the second original light detecting signal to generate a second light detecting signal; and a driving and determining circuit, configured to determine signal intensities of the first original light detecting signal and the second light detecting signal.