The invention discloses a ring current injecting and confining pressure reducing drill bit which comprises a drill bit body and a ring current injecting device. The drill bit body is provided with a plurality of knife wings. A chip discharge groove is formed between every two adjacent knife wings. Each knife wing is provided with a row of cutting teeth. A center runner is formed in the drill bit body in the axial direction. Multiple spray runners communicated with the center runner are formed in the drill bit body. A water outlet of each spray runner is provided with a drill bit face nozzle. A reverse injection channel is formed in the drill bit body. The ring current injection device comprises a ring-shaped injection sleeve and an injection pump. A ring-shaped cavity is formed between the ring-shaped injection sleeve and the outer wall of the drill bit body. The ring-shaped cavity is communicated with a liquid outlet of the reverse injection channel. The injection pump comprises an injection pipe and an injection nozzle. The drill bit enables pressure of the well bottom to be low, the purpose of reducing confining pressure of the working face of the drill bit is achieved, the pressing and holding effect is reduced, and the mechanical drill speed of drilling is remarkably increased.