Abstract: A light source assembly mechanism includes two sets installed at two ends of an LED lamp tube. Each light source assembly mechanism includes a base, a lamp tube side cap, a turning module side cap and a turning rod. The lamp tube side cap has one side fastened to one end of the LED lamp tube and another side running through the base via a fastening portion to fasten to a coupling portion formed on the turning module side cap. The turning rod runs through the turning module side cap to fasten to the lamp tube side cap. With the same modular elements used at two sides of the LED lamp tube, mold development cost can be reduced, and assembly processes can be simplified. Through turning the turning rod, illumination angle of the LED lamp tube can be adjusted to meet illumination requirements.