A LED light tube includes LED chips mounted on a substrate, a first fluorescent layer, a second fluorescent layer and a package housing. The LED chips emit a blue light. The first fluorescent layer has a first side facing to the LED chips for converting the blue light to a red light. The second fluorescent layer has a first side attached to a second side of the first fluorescent layer for converting the blue light to a red light emitted from a second side of the second fluorescent layer. The package housing holds the substrate and the first fluorescent layer.