The invention discloses a continuous filament prepreg 3D printing spray head and a 3D printer and a printing method thereof. The continuous filament prepreg 3D printing spray head comprises a rotating mechanism, a fixed support, a heat dissipation device, a heating device, a guide channel and pressing wheels. The heat dissipation device is screwed to the lower end of the fixed support, the heating device is connected to the lower end of the heat dissipation device, the guide channel sequentially penetrates the fixed support, the heat dissipation device and the heating device and used for downwards supplying prepreg, and the pressing wheels are arranged at the lower end of the heating device, distributed on the two sides of the guide channel and used for compacting the continuous filament prepreg which is in a molten state. The fixed support is provided with a feeding device, a shearing mechanism and a shearing and re-feeding device, wherein the feeding device and the shearing and re-feeding device are used for providing power for downward feeding, and the shearing mechanism is used for shearing off the prepreg according to needs. By means of the continuous filament prepreg 3D printing spray head and the 3D printer and the printing method thereof, continuous filament prepreg 3D printing is achieved, the overall strength and the interlaminar shear strength of non-metal 3D printing are improved, and the technical difficulty of continuous filament prepreg structural component forming is lowered.