The present disclosure provides a backlight module and a liquid crystal display using the same. The backlight module includes a light guide plate, a light source and a plurality of light extraction gratings. The light source is disposed at an end of the light guide plate. A plurality of light extraction gratings are disposed on a light emission surface of the light guide plate, and are arranged in an array. The plurality of light extraction gratings are divided into a plurality of regions arranged at equal intervals in a direction from the end of the light guide plate near the light source to another end of the light guide plate away from the of the light source, a gap between adjacent columns of two adjacent regions is a+b, where a is a gap between adjacent columns in the same region and b is a width of one light extraction grating.