Objective: To investigate the correlation between JNK signal and the apoptosis of VSMC as well as the expression of Cathepsin B and to explore the role of JNK signal in the development of cerebral aneurysm. Methods: Rat models of cerebral aneurysm were established and histopathologic changes of cerebral aneurysm and the apoptosis of VSMC were analyzed. Rat models were respectively subject to subcutaneous injection of Cathepsin B si RNA and JNK inhibitor SP600125. Western blot technique was used to detect the expression of proteins like Cathepsin B, Caspase-3, and p-JNK. Spearman’s rho was used to examine the correlation between p-JNK and Cathepsin B, as well as the expression of relevant proteins. Results:The success rate of modeling rats with cerebral aneurysm was 88.75%. After the respective injection of Cathepsin B si RNA, SP600125 and their combination, the cell densities of VSMC of rats with cerebral aneurysm all increased significantly(P<0.05 or P<0.01), but the apoptosis rate of VSMC decreased significantly(P<0.01). Compared with normal rats, the expression of Cathepsin B, Caspase-3 and p-JNK in cerebral aneurysm models increased significantly. Effectively intervening Cathepsin B genes with Cathepsin B si RNA could significantly inhibit the expression of Cathepsin B and Caspase-3, but hardly influence the expression of p-JNK. JNK inhibitor SP600125 had no influence on the expression of Cathepsin B and Caspase-3, but effectively inhibited the expression of p-JNK. In cerebral aneurysm tissues, positive correlation was observed between the expression of p-JNK and Cathepsin B, the correlation coefficient was r=0.640. Conclusion: After the attack of cerebral aneurysm, proteins like Cathepsin B, Caspase-3 and p-JNK are all involved in the apoptosis of VSMCs. This process may be realized by Cathepsin B which activates the apoptosis mechanism of Caspase-3 and mediate the apoptosis of VSMC through the JNK signaling pathway. Therefore, silencing Cathepsin B gene or inhibiting the conduction through JNK signaling pathway can mitigate the apoptosis of vascular smooth muscle cells in cerebral aneurysm. Methods: Rat models of cerebral aneurysm were established and histopathologic changes of JNK signal in the development cerebral aneurysm and the apoptosis of VSMC were analyzed. Rat models were respectively subject to subcutaneous injection of Cathepsin B si RNA and JNK inhibitor SP600125. Western blot technique was used to detect the expression of proteins like Cathepsin B, Caspase-3, and p- JNK. Spearman’s rho was used to examine the correlation between p-JNK and Cathepsin B, as well as the expression of relevant proteins. Results: The success rate of modeling rats with cerebral aneurysm was 88.75%. After the individual injection of Cathepsin B si RNA, SP600125 and their combination, the cell densities of VSMC of rats with cerebral aneurysm all increased significantly (P <0.05 or P <0.01), but the apoptosis rate of Compared with normal rats, the expression of Cathepsin B, Caspase-3 and p-JNK in cerebral aneurysm models increased significantly. Effectively intervening Cathepsin B genes with Cathepsin B si RNA could significantly inhibit the expression of JNK inhibitor SP600125 had no influence on the expression of Cathepsin B and Caspase-3, but actually inhibited the expression of p-JNK. In cerebral aneurysm tissues, positive correlation was observed between the expression of p-JNK and Cathepsin B, the correlation coefficient was r = 0.640. Conclusion: After the attack of cerebral aneurysm, proteins like Cathepsin B, Caspase-3 and p-JNK are all involved in the apoptosis of This process may be realized by Cathepsin B which activates the apoptosis mechanism of Caspase-3 and mediate the apoptosis of VSMC through the JNK signaling pathway. Thus, silencing Cathepsin B gene or inhibiting the conduction through JNK signaling pathway can mitigate the apoptosis of vascular smooth muscle cells in cerebral aneurysm.