Recombinant Anti-albumin x Anti-IL-6R Bispecific Antibody (Fab-VHH-Fc) requires expression of three polypeptide chains, encoding two heavy chains (Fc-containing chains) and one light chain, respectively. The Fab of anti-albumin antibody variable domain is fused to the Fc-knob domain with a hinge region and the same as the VHH of anti-IL-6R to the Fc-hole domain, or vice versa. The Fab-Fc and VHH-Fc fragments can be paired via the interaction of the Fc regions. This BsAb can act as PK-modulated receptor antagonist. It is designed for the research of Systemic lupus erythematosus (SLE); Rheumatoid arthritis (RA).