A method for forming an organic light emitting diode array is provided. A substrate is provided. A plurality of first electrodes is formed on a substrate surface. A patterned mask layer is disposed on the substrate surface to cover the substrate and expose at least a portion of each first electrode. An evaporating source is provided. The evaporating source comprises a carbon nanotube film structure and an organic semiconductor material. The evaporating source is spaced from the plurality of first electrodes. The carbon nanotube film structure is heated to gasify the organic light emitting material and form a plurality of organic light emitting layers on a exposed surface of the plurality of first electrodes. A plurality of second electrodes are formed on a surface of the plurality of organic light emitting layers. The patterned mask layer is removed to form an organic light emitting diode array.