Abstract: This study was conducted to investigate the effect of addition of soybean oil in dietary on concentrations of conjugated linoleic acid and intermediates of ruminal biohydrogenation of mature goat in vitro by batch culture. The addition level of these soybean oil were 0(control group ) and 100 mg/flask, respectively. Results indicated that the cis-9, trans-11 CLA content of soybean oil supplementation treatment was significantly（P＜0.05）higher than that of the control all the time, and which reached its maximum after 8 hours’ incubation (6.05 mg/g DM). And the trans-10, cis-12 CLA content of soybean oil supplementation treatment was also significantly（P＜0.05）higher than that of the control all the time, and which increased gradually, with the extension of incubating time. The total CLA content of soybean oil supplementation treatment reached its maximum after 16 hours’ incubation (11.61 mg/g DM). During in vitro study, that trans-11 C18∶1 and trans-10 C18∶1 were accumulated with treatment of soybean oil, and the treatment was abstractly higher than the control (P＜0.05). The total trans-C18∶1 content of soybean oil supplementation treatment increased gradually, with the extension of incubating time, while the total cis-C18∶1 content of soybean oil supplementation treatment decreased gradually.