The cDNA encoding glial cell-derived neurotrophic factor (GDNF) was isolated from the human astrocytoma cell BT-325. GDNF was efficiently expressed in E.coli. The recombinant protein was purified. The renaturation occurred in the presence of sodium tetrathionate system. In order to study the biological activity of the recombinant protein, the effects of rhGDNF on the dorsal root ganglion (DRG) of chicken embryo (8 d), motor neurons of rat embryo (14 d) spinal cord and glial cell were explored. The results show that rhGDNF promotes the growth of neurite of DRG, increases the number of survival motor neurons cultured for 3 d, 7 d, 14 d and 21 d, respectively, and promotes glial cell proliferation.