A nozzle for a gaseous fuel mixer comprises a straight segment pipe, a spray head segment and a connecting segment connecting the straight segment pipe with the spray head segment. The diameter d0 of the straight segment pipe is larger than the diameter d1 of the maximum section of the spray head segment. The connecting segment is an arc connecting segment. The spray head segment is provided with multiple spray openings, and the multiple spray openings are arranged in the radial direction and the axial direction of the spray head segment. The tail end of the spray head segment is a closed end, and the spray openings are formed in the closed face of the tail end of the spray head segment. The center lines of the multiple spray openings are arranged in a gradually expanding manner with the center line of the spray head segment as the center. The diameter d1 of the maximum section of the spray head segment is smaller than or equal to 1/3-1/2 of the diameter d0 of the straight segment pipe, that is, d1<=(1/3-1/2)d0. The sum of the sectional areas of the multiple spray openings is smaller than or equal to 1/5-1/3 time of the maximum sectional area of the spray head segment. The nozzle has the beneficial effects that disturbance is strong, and fuel does not flow back.