Abstract: This experiment was conducted to study the mechanism of FSH regulating GDNF expression in Sertoli cells. Different factors (inhibitor or activator) of signal pathway was added to Sertoli cells in vitro cutured, RTPCR and Western blot were used to detect the effect of FSH on GDNF expression. The result showed that: (1) FSH（50 ng·mL-1） could active ERK1/2 prominently along with a maximum stimulation at 2 h, the ERK1/2 reached a peak activity at 30 min. (2)dbcAMP（100 μmol·L-1）could not only increase the activity of ERK1/2 but also enhance the level of GDNF protein and mRNA with a maximum stimulation at 2 h. (3) While adding U0126 (10 μmol·L-1, MEK1/2 inhibitor) or H89 (10 μmol·L-1, PKA inhibitor) to culture medium, the results showed that the expression level of GDNF protein, mRNA and activity decreased apparently as compared with that in the cells treated with FSH alone. (4) The FSHactivated ERK1/2 in the cultured SC was timedependent, with a peak activity at 20 min. The activation of ERK1/2 by FSH was blocked by PKA inhibitor H89. These results indicate that FSH can activate ERK1/2 via cAMPPKA, which increase the expression of GDNF in Sertoli cell.