Objective：To explore the effects of dihydrotestosterone（DHT） and flutamide（Flu） on the gene expression of Mafb. Methods：Primarily cultured normal foreskin fibroblasts from children were treated with different concentrations of DHT and Flu，and then were tested for the transcription and expression of Mafb using RT-PCR，cellular immunofluorescence，and Western blot. Results：After treatment with DHT at concentrations of 3.0×10-8 mol/L and 3.0×10-6 mol/L，the mRNA expression of Mafb was significantly up-regulated in the DHT 3.0×10-6 mol/L group（0.594±0.045 vs. 0.444±0.007，P=0.005），but not significantly up-regulated in the DHT 3.0×10-8 mol/L group（0.372±0.003 vs. 0.444±0.007，P=0.145），as compared with that in the normal group. After treatment with 15 μmol/L Flu，the mRNA expression of Mafb was significantly reduced compared with that in the normal group（0.221±0.013，P=0.000）. Cellular immunofluorescence assay showed that the expression of Mafb was significantly up-regulated in the DHT 3.0×10-8 mol/L group and the DHT 3.0×10-6 mol/L group（0.046±0.004 and 0.076±0.003，respectively，P=0.010 and 0.000，respectively），but significantly down-regulated in the Flu group（0.006±0.002，P=0.009），as compared with that in the normal control group（0.027±0.006）. Similarly，Western blot results showed that the protein expression of Mafb was not significantly up-regulated in the DHT 3.0×10-8 mol/L group（0.146±0.001，P=0.960），but was significantly up-regulated in the DHT 3.0×10-6 mol/L group（0.598±0.087，P=0.000），while the expression was significantly down-regulated in the Flu group（0.066±0.002，P=0.040），as compared with that in the control group（0.163±0.001）. Conclusion：In the foreskin fibroblasts cultured in vitro，the gene expression of Mafb is regulated by DHT and Flu. Mafb，as a downstream regulatory protein of androgen receptor，may be an important mechanism in the androgen receptor signaling pathway to promote urinary tract development.