Antibody immobilization plays a key role in immuodetection in biosensors.Immobilizing the antibody effectively can help to improve the sensitivity, stability and specificity of the biosensor.In this paper, we investigate the methods used in antibody immobilization, including covalent immobilization, physical adsorbing, biotin-avidin immobilization, metal chelate immobilization, protein A immobilization and so on.Covalent immobilization stands out for its high stability and low non-specificity, becoming one of the most common methods for antibody immobilization.Protein engineering introduces functional protein to the constant region of the antibody which is helpful to the orient immobilization.