The invention relates to an aperture-controllable spray head of a three-dimensional (3D) printer. The aperture-controllable spray head comprises a feeding barrel and a discharge barrel, wherein a material spraying hole is formed in the bottom of the discharge barrel; the feeding barrel is communicated with the discharge barrel, and the feeding barrel is movably connected with the discharge barrel by an axial guiding device; when the feeding barrel and the discharge barrel move relatively, the aperture of the material spraying hole is increased or reduced, and the cross section of the material spraying hole is maintained to be a regular polygon which can be scaled in equal proportion. The invention also relates to a control method of the spray head of the 3D printer. According to the aperture-controllable spray head, the cross section of the material spraying hole of the spray head of the printer is the regular polygon and can be scaled in equal proportion along with the relative motion of the feeding barrel and the discharge barrel, so that the aperture of the material spraying hole can be adjusted according to the different area requirements of the printed products, and the cohesion and coherence of product printing can be guaranteed; the feeding rate of the spray head and the aperture of the material spraying hole are controlled in a cooperative way, and the height of the printed material is a constant value, so that the requirement for printing accuracy can be met, the printing efficiency is improved, and the objectivity of the printed products can be improved. The aperture-controllable spray head is applied to 3D printing.