A DNA fragment encoding human interleukin 4 was obtained by PCR from pORF-hIL4 plasmid. The amplified fragment was inserted into prokaryotic expression vector PQE60 and recombinant protein was expressed in E. Coli M15 by adding isopropyl-beta-D-thiogalactoside (IPTG). The hIL-4 protein was present as insoluble inclusion bodies in the bacterial extract. After denaturation of inclusion bodies with 5 mol/L guanidine hydrochloride, the supernate was diluted to get renaturized. Then dialysis and Ni chelating chromatography were used for purification. TF-1 proliferation assay of recombinant human interleukin 4 was performed, and then rhIL-4 was fit to be used for proliferation of human dendritic cells from monocyte in vitro.