Organic light emitting diodes (OLEDs) is one of the most potential display technologies in the flat panel display (FPD) field, and its applications include simple monochrome largearea lighting to full color, video-capable graphics displays and so on. As organic materials are susceptible to humidity and oxygen, encapsulation is a key issue for OLED device reliability. In the present paper, two kinds of OLED samples have been studied; one encapsulated by adhesive matrix with fillers, and one without encapsulation. Variation of the electrical parameters of the OLED samples with respect to exposure time has been measured. The primary experiment investigation was carried out for the OLED sample sealed with an anisotropic conductive adhesive. Encapsulation material analysis, such as choices of different fillers/absorbent in the adhesive matrix, optimization of polymer matrix etc., will be conducted in future work.