The appearance of black zone on the surface of white light-emitting diode (LED) with phosphor layer has greatly affected light conversion and extraction. Using micro-area analytical tools such as cutting section, scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), the acceleration stress test for current and temperature is carried out and the blacking phenomenon for part of the chip aging surfaces is analyzed. The experimental results show atomic number ratio of C to Si in blackened LED is 13.21, higher than that of the unchanged (8.45). There is a main cause about LED encapsulation failure that organic materials can degrade and carbonize in high temperature and lighting conditions, which is verified. And therefore, lighting effect cannot be ignored. But the chip has nothing to do with the failure. Interface stress induced by the mismatch of the expansion coefficient of the chip and packaging materials, photo-degradation and optic-thermal coupling resulted from long time blue-light illumination make the devices disastrously invalid.