A method for preparing a light-emitting layer, the light-emitting layer, an organic light emitting diode (OLED) device, and a display apparatus are provided. The light-emitting layer is prepared by preparing a host material containing a first photocrosslinker group and a guest material containing a second photocrosslinker group. The host material and the guest material are mixed in a solvent to form a mixture. The mixture is coated, annealed, and UV-irradiated on a substrate to form the light-emitting layer. As such, the disclosed light-emitting layer is prepared by the polymerization after being on the substrate. The light-emitting layer has a mesh structure. The mesh structure improves energy transfer between the host material and guest material and increases the lifespan of the resultant OLED device and OLED display apparatus.