A three-stage power adjustable Light Emitting Diode bulb includes a first resistance and a second resistance which is electrically connected to the first resistance in parallel. The first resistance and the second resistance are connected to a rectifier. Multiple Light Emitting Diode units and a limiting resistance are connected between the positive and negative poles of the rectifier. The Light Emitting Diode units each have multiple Light Emitting Diodes. The electric energy consumption of the Light Emitting Diode bulb is reduced and the life of use of the Light Emitting Diode bulb is prolonged. The resistance value of the first and second resistance can be adjusted to have different luminous powers.