An LED lamp includes a post (10), a heat sink (20) enclosing the post, an LED module (30) mounted on the post, a holder (40) secured on the LED module, and a lens (50) covering the holder. The heat sink is formed by a plurality of separated fins assembled together. Each fin comprises an outer portion (22) and an inner portion (24). An inner edge of the outer portion abuts interferingly against a periphery of the post, and a bottom of the inner portion contacts a top surface of the post. Heat generated by the LED module is conducted through the post to the plurality of fins, which dissipate the heat to the ambient air.