The liquid crystal day & night mirror with excellent reflective characteristics has been developed.The day & night mirror using Guest-Host liquid crystal devices improves the performance of rear view mirrors.Effects of primary factors on reflective characteristics of the liquid crystal day & night mirror have been investigated. Results are as follows. (1) The reflective characteristics at wavelength of about 555 nm are important for the selection of liquid crystals and dichroic dyes. (2) The reflective characteristics are improved by decreasing the reflectivity of glass substrate. (3) The reflective characteristics are improved by increasing the reflectivity of reflector.