Lumen decay of LEDs is affected by time, junction temperature and input current. In LED lamps, both temperature and input current vary with time due to driver's degradation and temperature change of lamps. This paper proposes a lumen decay prediction method which considers effects of operation time, temperature and current by taking the interaction of LED and driver performance into account. In particular, a lumen decay model for LED source with consideration of the ever changing current and temperature is developed and validated experimentally. Several scenarios are analyzed theoretically by applying different assumptions.@en