An LED flat lamp including a housing with a light-emitting area at the bottom thereof. The internal side thereof undergoes a reflexion treatment. At least one LED is disposed within the housing. A power connector is extended from the LED to the outside. The LED is installed on a circuit board. A light guide plate is installed at one side of the LED within the housing. The light exit side of the light guide plate is provided with a microstructure for a uniform light exit. Moreover, an optical film unit is attached to the bottom of the light guide plate such that the light-emitting area of the housing is covered with the optical film unit. The optical film unit consists of one or several brightness enhancement films and one or several diffusers. In this way, the problem of glaring light directly emitted by the prior art is resolved. The LED flat lamp in accordance with the invention can emit a non-glaring light and can be modularized into a standardized product.