LEDs have been used extensively in the mobile device, automobile, and general lighting because they are semi-permanent, long life, less power consumption, reliable and environmentally friendly. In this paper, the accelerated degradation test(ADT) for a general lighting 4W LED Lamp using external converter is considered. The conditions of ADT are high temperature and high humidity. We show that its life time is log-normally distributed with same parameters under both a normal condition and an accelerated condition, and also derive an accelerated factor.