The invention relates to the technical field of microelectronics, in particular to an OLED device structure and a fabrication method thereof. The OLED device structure comprises a glass layer, a firstmetal layer, a first insulation layer, a semiconductor layer, a second insulation layer, a second metal layer, a third insulation layer, a first organic layer, a third metal layer, a second organic layer, a fourth metal layer and a third organic layer. A groove is formed in the first organic layer, the vertical cross section of the groove is in an arc shape, a microstructure similar to a concavemirror can be formed, the concave mirror is high in condensation effect, the light ray utilization rate of an OLED light-emitting layer can be effectively improved, and the display effect of a panel is improved. In the OLED device structure designed by the scheme, the current intensity can be reduced under the condition that same brightness is achieved, the service lifetime of a light-emitting material is prolonged, and the device brightness is more excellent under the same light-emitting area.