The present invention relates to a lighting device with switchable day/night illumination mode, comprising: a main controlling unit, a driving unit, a lighting unit, a light filtering unit, an illumination mode switching unit, and a power management unit, wherein the lighting unit is coupled to the driving unit and has a plurality of light-emitting devices. Moreover, the main controlling unit is used for controlling the driving unit, so as to drive the lighting unit output a visible light. In addition, the illumination mode switching unit is used for controlling the light filtering unit to show and cover the light-emitting surface of the lighting unit, so as to filter the visible light and make the visible light become a visible light with a specific wavelength; wherein the visible light with specific wavelength causes the smallest excitation to human sympathetic. Thus, using the visible light with specific wavelength as illumination light at night can not only assist users in reading, but also avoid from exciting users' sympathetic and causing melatonin suppression.