Social anxiety is a common problem that usually emerges at puberty, during which great developmental changes occur both in the brain and mental state. However, little is known about the influence of social anxiety on adolescents' brain and behavior. The present study investigated the neural basis of social anxiety using voxel-based morphometry (VBM) and functional connectivity analysis. Then we investigated whether social anxiety is associated with attention bias. Furthermore, we investigated the neural basis of this association. Finally, longitudinal data was used to test if these biomarkers could predict social anxiety. The results indicated that social anxiety is positively associated with the grey matter volume (GMV) of orbital-frontal cortex (OFC), and the functional connectivity (FC) of OFC-amygdala. Mediation analysis revealed that the relationship between social anxiety and attention avoidance is partly mediated by the FC of OFC-amygdala. Finally, the present study demonstrated a close relationship between FC of the OFC-amygdala, the GMV of the OFC and the individual's social anxiety one year later. The present study suggested the aberrant structure of OFC and its connectivity with amygdala as the neural underpinning of social anxiety, which might serve as a compensatory mechanism to decrease attention avoidance and promote effective emotion regulation.