Gold nanoparticles labeled stretavidin can bind to trace antigens, antibodies and receptors, and has a wide range of applications in biological detection and biosensors. Biotin-linked streptavidin can be applied to nano-gold technology. The principle is that positively charged streptavidin is labeled with negatively charged gold nanorods-streptavidin and gold nanoparticles-streptavidin, and then tightly bound to biotin together. This allows the detection signal to be amplified on the basis of only nano-gold labels or only biotin labels.