Abstract: Leydig cells were isolated from the testis of 3 week old Rongchang piglets. Its activity, purity and function were qualified before being cultured in vitro. Then, they were respectively treated with 0.125, 0.25, 0.5, 1 and 2 μmol L-1 c-jun ASODNs and the expression of c-jun mRNA were detected by FQ-PCR. To study the effect of c-jun on proliferation of elemental status leydig cells in piglets, the leydig cells had been treatedwith c-jun ASODNs and the growth inhibition ratio of leydig cells were detected by MTT method and cell cycle phase distribution were examined by flow cytometer analysis. The FQ-PCR assays results indicated that c-jun mRNA expression decreased with the rise of c-jun ASODNs concentration. Only 0.125 μmol L-1 c-jun ASODNs could reduce the expression of c-jun gene significantly (p<0.01). And the expression no longer went down when the concentration was up to 1 μmol L-1. Through MTT analysis, it is found that c-junASODNs could inhibit the growth of leydig cells significantly (p<0.01). There is a positive correlation between c-jun ASODNs concentration and growth inhibition ratio of leydig cells (r = 0.8966).