An LED lamp includes a bracket and a heat sink mounted on a top side of the bracket. The heat sink includes a base. A plurality of LED module assemblies is mounted to a bottom surface of the base of the heat sink. Each of the LED module assemblies includes a heat absorbing plate located below the bottom surface of the base of the heat sink, an LED module mounted on a bottom surface of the heat absorbing plate and a heat pipe interconnecting the bottom surface of the base and a top surface of the heat absorbing plate. The heat pipes are U-shaped and horizontally positioned and have different heights.