The present invention provides a backlight module structure, which includes a backplane (1), a light guide plate (3) arranged inside the backplane (1), and at least two backlight sources (5) arranged inside the backplane (1). The backplane (1) includes a bottom board (11) and a plurality of side boards (13) perpendicularly connected to the bottom board (11). The light guide plate (3) includes at least two sub light guide plates (4) that are sequentially connected in such a way that a recess (33) is formed in a connection between two adjacent ones of the sub light guide plates (4). The recess (33) has an opening facing the bottom board (11). The bottom board (11) includes a protrusion (111) formed thereon to correspond to the recess (33). The at least two backlight sources (5) are mounted on the protrusion (111) and located between the recess (33) and the protrusion (111) so that the two backlight sources (5) emit lights respectively toward the two adjacent sub light guide plates (4). The backlight module structure suits the need for size enlarging of light guide plates and also better achieves dynamic light adjustment, reduce energy consumption, and improve optical quality.