The present disclosure provides a projection system and a light screen generating device thereof. The light screen generating device includes a movable carrier module, a first light-emitting module, and a second light-emitting module. The first light-emitting module includes a plurality of first light-emitting structures disposed on the movable carrier module. Each of the first light-emitting structures generates an invisible light screen, and the invisible light screens respectively generated by the first light-emitting structures are mated with each other to form a spliced invisible light screen for increasing light emission uniformity. The second light-emitting module includes a second light-emitting structure that is disposed on the movable carrier module and that generates a visible light screen parallel to and overlapping the spliced invisible light screen.