Molecularly imprinted polymeric monolithic (MIPM) fiber presents a new technique of solid-phase microextraction that focuses on specific selectivity in a target analyte.However, the inner mechanism of increasing the specific selectivity is not well understood.Optimizing the MIPM fibers constitutes and the analytical conditions are general procedures to obtain better selectivity.Here we show that controlling the surface of a MIPM fiber is a new way to improve its specific selectivity.We fabricated sulfadimidine-imprinted polymeric monolithic fibers using two kinds of molds, the polyfluortetraethylene (PTFE) capillary and the silica capillary.A mixture of sulfadimidine, sulfamerazine, sulfadiazine and sulfametoxypirydazine were used to test the specific selectivity of the fibers in sulfadimidine.