The present invention provides a fusion protein inhibiting TACI-BAFF complex formation and preparation method therefor and use thereof. Specifically, the fusion protein of the present invention is of high biological activity for blocking BAFF / APPRIL, and may significantly lower the serum IgM concentration in normal Balb / c mice as well as the serum IgM and IgE concentration in C57 / B6 mice with asthma. The TACI-Fc fusion protein of the present invention may be used in the treatment of autoimmune diseases, including asthma, systemic lupus eythematosus and rheumatoid arthritis, etc., and may also be used in the treatment of B cell enrichment-related diseases, including multiple myeloma, chronic lymphocytic leukemia, macroglobulinemia and plasmacytic leukemia, etc.