An LED lamp for providing a relatively large luminous flux, includes a housing and a pair of LED units mounted in the housing. The two LED units are separated from each other by a clapboard set in the housing. Each LED unit includes a plate, a plurality of LED modules disposed on the plate and a cover laying on the plate and cover the LED modules. The cover forms a plurality of vents to expose LEDs of the LED modules therein. A plurality of first screws extends through the LED modules and the plate to secure them together, while a plurality of second screws extends through the plate, the cover and the housing to fix the whole LED unit to the housing. Each LED module has a printed circuit board and a plurality of LEDs on the printed circuit board.