Aim To investigate the role of plasminogen activator inhibitor 1 (PAI 1) antisense RNA in influencing plasma fibrinolytic activity, and regulating the expression of PAI 1 and the process of atherogenesis in rabbits. Methods PAI 1 antisense RNA recombination plasmid was constructed by using eukaryotic cell expression vector pcDNA3.1. Thirty rabbits were classified into 4 groups. Control group (n=7) was fed with a normal diet. Atherosclerosis (As) group (n=7) was fed with a high cholesterol diet. Plasmid treatment group (treatment group, n=9) was fed with a high cholesterol diet and injected with PAI 1 antisense RNA recombination plasmid (20 μg/kg ) into the abdominal subcutaneous tissue weekly. Plasmid group (n=7) was fed with a normal diet and injected with PAI 1 antisense RNA recombination plasmid (20 μg/kg ) into the abdominal subcutaneous tissue weekly. Then the activities of tissue plasminogen activator (t PA), PAI 1, and serumal lipid were detected. PAI 1 protein expression in tissues was tested by immunohistochemistry. Lastly, the extent of atherosclerosis was observed by patho anatomy. Results In plasmid treatment group and plasmid group, the activity of PAI 1 in plasma decreased while that of t PA increased. Although there were no differences between As group and plasmid treatment group in the activities of PAI 1 and t PA at the beginning of the study (p>0.05), in the end the differences were significant (p<0.05). PAI 1 protein only existed in endothelial cells in plasmid treatment group, while in As group, it not only existed in both endothelial cells and smooth muscle cells but also outnumbered the former. Compared with As group, the intima of the arterial vessel was thinner in plasmid treatment group. Plasmid treatment group had a lower lipid count (serum triglyceride and cholesterol) (96±42 mg/L vs 123±12