A backlight module and a display device is disclosed. The backlight module includes a backplate, a light board framework, and assembled light board arranged in sequence. The assembled light board include multiple light boards with a seam formed between adjacent light boards. The light board framework is arranged on the backplate and includes a main body defining multiple mounting grooves provided in a number equal to the number of the light boards in the assembled light board. Each of the light boards is installed in one of the mounting grooves. A supplementary light-emitting diode (LED) is disposed between adjacent mounting grooves to supplement light for the seam between every two adjacent ones of the light boards.