Objective: To construct an immune alpaca phage display library, in order to obtain a single domain anti-BAFF (B cell-activating factor) antibody. Methods: Using phage display technology, we constructed an immune alpaca phage display library, selected anti-BAFF single domain antibodies (sdAbs), cloned three anti-BAFF single-domain antibody genes into expression vector pSJF2, and expressed them efficiently in Escherichia coli. The affinity of different anti-BAFF sdAbs were measured by Bio layer interferometry. The in vitro biological function of three sdAbs was investigated by cell counting kit-8 (CCK-8) assay and a competitive enzyme-linked immunosorbent assay (ELISA). Results: We obtained three anti-BAFF single domain antibodies (anti-BAFF64, anti-BAFF52 and anti-BAFFG3), which were produced in high yield in Escherichia coli and inhibited tumor cell proliferation in vitro. Conclusion: The selected anti-BAFF antibodies could be candidates for B-cell lymphoma therapies.