Objective To construct secretory IgA(sIgA)based on the previously screened IgG neutralizing antibody ZW2G10 against SARS-CoV-2,evaluate its activity and find out about the biodistribution of sIgA in ICR mice after nasal administration.Methods After expression,purification,and identification,sIgA was evaluated for its binding and neutralizing activity through ELISA and pseudovirus-based neutralization assays.SIgA was coupled with Alexa Fluor 750 dye and administered to mice via nasal administration.In vivo imaging was used to observe the biodistribution of sIgA.After dissection of the mice,the biodistribution of sIgA in various tissues and organs was observed.Results Compared with IgG,sIgA retained the binding ability to SARS-CoV-2 S proteins,and its neutralizing ability was enhanced.After nasal administration of a single dose of 1 mg/kg,sIgA could be retained in the lungs of mice for more than 72 hours.SIgA could be detected only in the nasal cavity and gastrointestinal tract within 8 h of administration,but not in the heart,liver,kidney,spleen,brain,bladder or blood.Conclusion In this study,a universal and efficient sIgA expression system has been established.sIgA can effectively target the respiratory tract and lungs after nasal administration.SIgA is expected to become a potential drug that provides immediate passive immune protection.