The invention relates to the technical field of power equipment, in particular to a premixing nozzle and a gas turbine. The premixing nozzle comprises a center body, an inner annular wall, an outer annular wall and a rotational flow device, wherein an independent diffusion fuel channel is formed between the inner annular wall and the outer annular wall. Fuel in the diffusion fuel channel is divided into two streams, one is directly and axially ejected into a flame tube through ignition fuel ejection holes and forms a local low-speed area or backflow area downstream a fire-stabilizing bluff body, and the other is directly and radially ejected into the local low-speed area or backflow area downstream the fire-stabilizing bluff body through fire-stabilizing fuel ejection holes. Flame stability is improved by the fire-stabilizing bluff body and fuel ejected through the fire-stabilizing fuel ejection holes, and ignition and stabilization of premixing flame of the nozzle can be realized more reliably so as to improve ignition performance of the premixing nozzle. Meanwhile, the structure at the outlet of the nozzle is structurally improved, and the effect of easy machining and maintaining of the structure is realized.