Disclosed is a prepreg, including a reinforcing material and a polymer, wherein the polymer is polymerized from a monomer, an oligomer, or combinations thereof of an organic rod-like molecule. The organic rod-like molecule has at least one photo-polymerizable group. The organic rod-like molecule has the magnetic susceptibility along its long-axis direction (M1) greater than the magnetic susceptibility along other directions (M2), and the magnetic susceptibility ratio (M1/M2) is greater than 0.01 and less than 1.