An LED display device includes a substrate and an LED encapsulation unit disposed on a side of the substrate, the LED encapsulation unit includes an LED stent and an LED chip encapsulated in the LED stent, a epoxy resin encapsulates the side of the substrate on which the LED encapsulation unit is disposed and the LED encapsulation unit to form a protection layer shielding the LED encapsulation unit. The epoxy resin completely encapsulates the substrate and the LED encapsulation unit to protect effectively the substrate and the LED encapsulation unit, which is sufficient to resist severe environment. Compared with the prior art, the service life of the LED display device is effectively prolonged, cost is reduced. The invention also provides a molding module for preparing the LED display device, and a preparation method thereof.