We investigate the proton collimation of foil-and-tube structured target with two-dimensional particle-in-cell simulation. The foil backside and the adjacent tube are coated with a thin hydrocarbon layer (HCL). It is found that the tube-wall HCL protons pulled out by the transverse space-charge field of the laser expelled electrons in the tube hollow can self-consistently modulate the field, which in turn affect the dynamics of foil-back HCL protons, such that a well-collimated proton beam with 0.9∘ divergence angle is produced if the tube is cone-like.