A unique four-way ligation strategy was developed for rapid construction of a full-length antibody library.A mammalian expression vector was constructed that contained dual mammalian expression cassettes and sequences recognized by the unique restriction enzymes BsmBI, BstXI, and SfiI, Both full-length light-chain and variable domain of heavy-chain genes were inserted into the vector in one step by four-way ligation, and fulllength bivalent antibodies were displayed on mammalian cell surfaces. Using this strategy, only 2 weeks were required to successfully construct high-quality, full-length human antibody libraries.