Due to its small size and stable, single-domain nature VHHs or single-domain antibody (sdAb) has become an ideal building block in cell therapy and achieved encouraging success clinically, such as in the case of CAR-T therapy based on anti-BCMA VHH (CARVYKTI® by Legend/J&J). However, VHH discovery based on the conventional immunized phage library is sometimes hampered by the poor sequence/epitope diversity and low immune response due the high AA sequence homology of the target protein between human and the host species. To address these limitations, here in this report, we present an alternative approach utilizing an alpaca naïve VHH library combined with antibody engineering by affinity maturation.