The failure mechanism of GaN based green LED chip was studied by elect rical accelerated aging method.After aging for 424h at 60mA current,the optical power of LED dec reased with the increasing aging time,but the trend of optical power decay at low measuring current levels is mo re obvious than that at high measuring current levels.The aging stress does not affect the forward-bias ele ctrical characteristics.However,the reverse-bias current increased rapidly with the increasing aging time.The auth or considers that the defect energy level in the active region increases with the aging time.It is believed that th e defect in LED by electrical stress acted as the effective trap in the forward voltage,which increased the lifetime of carriers and reduced the probability of the radiation recombination.When the voltage is reversed,the de fect acted as the channel of leakage current,which increased the reverse current.