The fabrication method for novel polymer imaging fiber is developed. The theory of light propagation in fiber and fiber design is expatiated, which is the guide for developing imaging fiber. The material of polymethyl methacrylate (PMMA) is heated and extruded in a hexagon mold as microstructured fiber preform. The holes in it are filled with polystyrene (PS) fibers. It is the first preform used for heat-stretch and stack-fusion to form a second preform. Then the second preform is heat-stretched to obtain imaging fiber with diameter of 0.22 mm and single fiber diameter of 3 μm. It is ultrahigh resolution imaging fiber, by which the microscale of 10 μm can be discerned. The method of one-step stack is used to stack 7200 pieces of customized polymer fibers as the multicore imaging fiber preform. The customized fiber with diameter of 0.25 mm and coating thickness of 20 μm is fused together. The preform is heat-stretched to form imaging fiber of 2 mm diameter and 20 μm single fiber diameter. It is found that the dust adsorbed on the fiber face seriously affects fiber′s structure and image quality.