The invention particularly relates to a hollow polyacrylonitrile-based carbon fiber and a preparation method. The outer diameter of the hollow polyacrylonitrile-based carbon fiber is 10-20 microns, the degree of hollowness is 10%-35 %, the shape factor is 1.00-1.01, the tensile strength is 3.0-4.0 Gpa, the tensile modulus is greater than 250 Gpa, and no obvious bonding mark exists on the surface.According to the method, a binary or ternary copolymerization system taking acrylonitrile as a main monomer is adopted to cooperate with an arc slit type spinneret plate dry-jet wet-spinning method for spinning, a hollow carbon fiber precursor can be obtained, the precursor can be treated by an oxidation carbonization process to obtain the hollow polyacrylonitrile-based carbon fiber, the surfacesof the precursor and the carbon fiber are smooth, and the section irregularity is low. According to the method, the dry-jet wet-spinning spinning technology is adopted, so that the spinning speed is high, and the production efficiency is improved; the surfaces of the precursor and the carbon fiber are smooth and compact, the section irregularity is low, and the performance is excellent; the process is simple and feasible, high-power drafting can be realized at a drying stage in the solidification forming process, and fine denier achievement of the fiber diameter is facilitated; arc-shaped liquid flow is bonded into a hollow structure at the air drying stage without obvious closing traces.