Embodiments provide a backlight control method and device and a liquid crystal display device, which relate to the liquid crystal display field and are used to achieve the purposes of meeting the requirements on different image quality enhancements in different display regions of the liquid crystal screen and improving the display quality and the sense of display layering of pictures. The method comprises: dividing n backlight subregions into m backlight regions; acquiring an average backlight value of each backlight region among the m backlight regions; searching, from a pre-acquired gain search table, a gain value corresponding to the average backlight value of each backlight region among the m backlight regions; adjusting backlight values of backlight subregions contained in each backlight region correspondingly according to the gain value corresponding to each backlight region; and outputting adjusted backlight values of the n backlight subregions. The embodiments are applicable to backlight adjustment scenes.