The invention provides a hot rolling device, a light guide plate, a preparation method of the light guide plate and a backlight module. The hot rolling device is provided with a quantum dot supplying unit, and light guide dots can be distributed on the medium-sized thin light guide plate by a hot rolling mode. The light guide plate, the preparation method of the light guide plate and the backlight module have the advantages that the density of the light guide dots (namely quantum dots) on the light guide plate can be controlled via the configuration of a microstructure on a roller; the content of the quantum dots of each light guide dot can be actually controlled according to parameters such as the pressure of the quantum dot supplying unit, the viscosity of a quantum dot mixture, the rotation speed of the roller and the like, and the light guide dots are effectively configured on the medium-sized thin light guide plate.