In order to meet the requirements of high sensitivity and specificity of biomedical research, a new optical nanofiber biosensor using gold nanorods (GNR) as amplification labels is reported, based on extinction property of GNR. Optical influence of GNR attached to the surface of fiber is studied. Single GNR is successfully resolved in experiment. In this nanofiber biosensor, a sandwich assay strategy is utilized for detection. The limit of detection (LOD) of this sensor for Goat- IgG is 0.02 ng/mL in PBS, which shows a great performance in sensitivity and specificity. The biosensor, reported in this work, has the advantages of simple detection scheme, fast response time, and ease of miniaturization, which might make this biosensor a promising platform for clinical cancer diagnosis, food safety detection and environmental monitoring.