An LED lamp includes a lamp base, a heat sink mounted on the lamp base and a plurality of LED modules thermally contacting with the heat sink. The lamp base defines a plurality of vents therein. The heat sink includes a central cylinder and a plurality of fins spaced from and surrounding the cylinder. The cylinder defines a through hole therein, which communicates with the vents of the lamp base and cooperates with the vents to form an air passage communicating with ambient air. An included angle is defined between each of the fins and a central axis of the cylinder. The LED modules are mounted on outmost ones of the fins of the heat sink, respectively.