Abstract: An electric conductivity-based biosensor electrochemically detects the concentration of tested objects via measuring impedance or capacitance variation of the tested objects. The biosensor comprises a substrate, two electric-conduction electrodes arranged on the substrate, an antibody adhesion layer arranged on a region of the substrate and a plurality of antibodies arranged on the antibody adhesion layer. The antibody adhesion layer is between the two electric-conduction electrodes. The antibodies are connected with a plurality of tested objects. The tested objects connected with the antibodies form an electric-conduction group contacting the two electric-conduction electrodes. The concentration of the tested objects can be provided via measuring impedance or capacitance between the two electric-conduction electrodes.