The invention relates to a T-shirt printing system adopting a rotary bracket and a cantilever beam spray printing device and a T-shirt printing method. At present, the T-shirt printing system adopting the rotary bracket and the cantilever beam spray printing device and the T-shirt printing method by which the T-shirt printing efficiency and the T-shirt printing quality can be greatly improved have not been invented. The T-shirt printing system comprises the rotary bracket; and a plurality of T-shirt supporting plates which can rotate along with the rotary bracket are arranged on the rotary bracket. The T-shirt printing system is characterized by further comprising the cantilever beam spray printing device; the cantilever beam spray printing device comprises a spray printing device rack, a printing mechanism and a cantilever beam; and one end of the cantilever beam is arranged on the spray printing device rack through a group of cantilever beam guide rail components, and an outrigger structure is formed at the other end of the cantilever beam and is directly erected at one side, facing the T-shirt supporting plates, of the spray printing device rack, so that actual printing areas of the T-shirt supporting plates are positioned in a printing area of the cantilever beam spray printing device. According to the T-shirt printing system and the T-shirt printing method disclosed by the invention, the T-shirt printing efficiency and the T-shirt printing quality can be greatly improved.