A method for manufacturing light emitting diode crystal grains includes steps of providing a first substrate; forming a buffer layer on the first substrate; forming a UV blocking layer on buffer layer; and forming a plurality of light emitting diode crystal grains on the buffer layer. The emitting diode crystal grains together form a wafer. An auxiliary substrate is provided and coated with an adhesive layer. The auxiliary substrate is pressed to the wafer, the adhesive layer fills gaps between the light emitting diode crystal grains, and solidifies the adhesive layer. The second surface is irradiated and gasified. The first substrate is thus separated from the UV blocking layer and the adhesive layer is dissolved, thus achieving a plurality of light-emitting diode crystal grains.