A liquid crystal display module, which can prevent corrugations of a reflection plate, and an assembling method thereof are disclosed. The liquid crystal display module comprises: a liquid crystal panel; a light source assembly; a light guide plate; a reflection plate; a support main; and a cover bottom, the reflection plate being disposed to be spaced a predetermined gap from the inner wall surfaces of the support main, the light guide plate being fixed to lateral stepped faces formed on a lateral inner wall surface of the supporter main while maintaining a first gap between the light guide plate and the reflection plate, and the light source assembly being fixed between an inner wall surface of a light incident portion of the support main and an incident surface of the light guide plate while maintaining a second gap between the light source assembly and the reflection plate.