A flexible organic light emitting diode (OLED) device and a manufacturing method thereof are provided. The manufacturing method includes forming a flexible base; forming a light emitting layer on the flexible base; evaporating a barrier material including a precursor polymer, a photoinitiator and a cross-linking agent on a surface of the light emitting layer; and irradiating a light beam on a surface of the barrier material during evaporating the barrier material, so as to form a barrier layer on a surface of the light emitting layer to block water and oxygen.