Is there any bus departing from Chadianzi Bus Station to Jiuzhaigou.

Yes, over 15 buses are scheduled daily from the bus station. The first bus leaves at 07:30 and the last one goes at 19:10. Generally, it is not that hard to get a ticket upon your arrival. If you insist in booking in advance, there is an official website of Sichuan Bus Transport. But it is only in Chinese. Yo may dial 400 660 8787 and try to book via phone. Good luck!