Hyaluronan-binding proteins (HABPs), the important structural components of extracellular matrices, served important structural and regulatory functions during development and in maintaining adult tissue homestats. A sensitive, specific and rapid-responsing immunosensor to probe hyaluronan-binding cartilage protein was presented in this work. The novel immunosensor supplied a label-free detection method for HABP, which was based on measuring the capacitance change in-between the unlabeled HABP (antigen) and rabbit-anti-HABP (Ra-HABP, antibody). The HABP immunosensor was prepared by covalently coup領(lǐng) Ra-HABP on an amine-self-assembled gold surface with glutaraldehyde. The capacitance change corresponding to the concentration of HABP, the target antigen, was evaluated by an electrochemical approach called potentiostatic-step in microseconds. The immunosensor showed a specific response to HABP in the range 10/1000 ng/ml. The presented work supplied a promising clinical screening method.