The present invention, pertaining to the field of plant cultivation, provides a plant growth control system and method. The system (100) comprises: an information collector (110), a processor (120) connected to the information collector (110), and a controllable light source (130); wherein the information collector (110) is configured to acquire growth information of a plant, the growth information comprising at least one of branch and leaf distribution information of the plant and flower distribution information of the plant; and the processor (120) is configured to determine, according to the growth information, a target irradiation position of the controllable light source (130) in the plant, and to control the controllable light source (130) to irradiate the target irradiation position in the plant.