Abstract: The aim of the present study was to express goat mature interleukin-4 gene in E. coli and to test the bioactivity of the recombinant protein. The mature GIL-4 (mGIL-4) was amplified using pMD18-T-pGIL-4 (pGIL-4, goat IL-4 complete sequence) as template by PCR. The recombinant plasmid of pET-32a(+) containing mGIL-4 gene was transformed into E. coli BL21, and induced by IPTG. The recombinant protein expressed in E. coli was purified by modified method and refolded. Lymphocyte transformation test was performed to detect the bioactivity of recombinant protein to stimulate the proliferation of T lymphocytes in goat’s peripheral blood mononuclear cells (PBMC). Sequence analysis of mGIL-4 demonstrated an open reading frame (ORF) of 339 base pairs encoding for 112 amino acids. The recombinant protein was approximately 31.3 kD and was mainly existed in the inclusion body. Through improved purification methods, highly purified recombinant protein was obtained. The bioactivity test proved that purified recombinant protein was able to significantly stimulate the proliferation of goat peripheral blood T lymphoblasts in a dose-dependent manner and the recombinant protein of 8 μg·mL^-1 presented the highest stimulation. The data provided foundations for the scale production and the application as adjuvant of the goat recombinant interleukin-4.