A reflective surface plasmon resonance（SPR） optical fiber sensor based on silver mirror reaction was developed,and a quick surface biological functionalization on the silver nanofilm was realized by dopamine self polymerization for monitoring of antigen-antibody interaction.A homemade SPR instrument was applied to investigate the effect of sensing length and various modification on the SPR signals.In order to enhance the sensitivity of the SPR optical sensor,the length of the sensing area was optimized.As the length of the sensing area increased,the sensitivity based on wavelength shift showed an obvious increase,while the sensitivity based on reflectivity shift did not have a distinctive change.The results showed that the fabricated SPR optical fiber sensor has a high sensitivity.When the sensing length is 1.5 cm,the sensitivity based on wavelength shift is 4 166 nm/RIU,while the sensitivity based on reflectivity shift is 99%/RIU.In addition,the SPR optical fiber sensors were further modified with antigen,and used to monitor the process of IgG antigen binding on biosensors.Significant wavelength shifts were found after every surface modification step,which indicated that dopamine modification to realize quick surface biological functionalization on silver nanofilm was feasible and the further biological functionalization was successful.By monitoring the binding process of IgG antigen and IgG antibody,a gradual red shift of the wavelength was found during the binding process,demonstrating the potential biological application of this biosensor.