Provided herein are nanobodies, polypeptides including the same, and uses thereof. The nanobody's variable region includes 3 complementarity determining regions (CDRs) and framework regions (FRs), where the CDRs are as follows: CDR1: Ser-Gly-Xaa11-Xaa12-Phe-Xaa13-Xaa14-Asn-Xaa15 (Formula I); CDR2: Xaa21-Thr-Xaa22-Xaa23-Gly-Xaa24-Thr (Formula II); CDR3: His-Xaa31-Asp-Glu-Xaa32-Arg-Xaa33-Ser-Xaa34-Trp-Thr-Thr-Ser-Asn-Xaa35 (Formula III). The nanobodies and their polypeptides exhibit high affinity and activity, specifically recognizing and binding AAV. Affinity agents prepared therefrom have strong AAV adsorption capacity, suitable for AAV affinity chromatography to facilitate its industrial application. They are also applicable to AAV detection, enabling simultaneous detection of empty capsids and viral particles.