Objective：To produce broad - spectrum nanobodies（Nbs）targeting severe acute respiratory syndrome coronavirus 2 （SARS - CoV - 2）and its variants，and establish a strategy for producing Nbs broad - spectrum neutralizing the virus and its various variants. Methods：Alpacas were immunized with the receptor-binding domain（RBD）of the SARS-CoV-2 wild-type strain（WT-RBD） to construct a nanobody phage library，and the library was screened by biopanning and ELISA with the RBD of the Delta variant（Delta- RBD）to select Nbs. The selected Nbs were expressed and purified using the Pichia pastoris system，and their properties and functions characterized by ELISA，biolayer interferometry，pseudovirus neutralization experiments，and molecular modeling and docking. Results：Four Nbs were obtained，all exibiting high affinity for WTRBD，while also effectively neutralizing DeltaRBD and the RBD of the Omicron variant（Omicron RBD），with Nb45 effectively neutralizing the pseudovirus of（Omicron -RBD）. We also found that the mechanism of these Nbs for neutralizing SARSCoV-2 and its variants may be related to interfering with the conserved sites on these RBD. Conclusion：The four Nbs obtained have great potential for prevention and treatment of SARS-CoV-2 and its variants，and the strategy established in this study can also be widely used for the preparation of Nbs broad - spectrum neutralizing viruses and their various variants.