An LED lamp includes a positioning frame base, LED bars, a light guide plate, a reflection sheet, an optical film, a power supply unit and a protective cover. The LED bars and the light guide plate are disposed at the inner side of the positioning frame base; the reflection sheet is stuck on one side of the light guide plate; the optical film is disposed on the other side of the light guide plate, and the protective cover is disposed over the optical film. The power supply unit is installed at the rear side of the positioning frame base for converting and supplying steady DC power for the LED bars. Different types of optical films can be selected for adjusting the lighting angles of the LED bars.