A two-level LED security light includes a light emitting unit, a power supply unit, a loading and power control unit, a light sensing control unit, a motion sensing unit and a time setting unit. The lighting-emitting unit includes an LED load which may be turned on or turned off by the light sensing control unit and controlled by the loading and power control unit. When the motion sensing unit detects an intrusion, the LED load is switched to a high level illumination for a predetermined time length adjustable by the time setting unit. The LED load is configured with a plurality of LEDs accommodating to the power supply unit wherein a voltage V across each LED is confined in a range Vth