Human Interleukin-11 (hIL-11) is a multifunctional cytokine which plays an important role in regulating the proliferation and differentiation of cells in the hematopoeitic, lymphoid system etc. To obtain the IL-11 cDNA, a primary culture of Chinese fetal lung fibroblast was prepared from fresh tissue. Then the human IL-11 cDNA without the N-terminal signal peptide sequence was cloned by RT-PCR from the cells induced by PMA. The sequence indicated that there are three bases different from those previously reported, but with no change of the amino acids. The cDNA was inserted into the 3' end of trxA gene in thioredoxin gene fusion expression system pTRXFUS to construct the trxA and hIL-11 fusion expression vector, and expressed in E. coli. The fusion hIL-11 accounts for more than 20% of the total bacteria proteins. The expression product is present in soluble forms and has the full biological and immunological activities.