There are buses to jiuzhaigou valley twice every day from Chengdu chadianzi bus station and Xinnanmen bus station. Although there are only about 450km from Chengdu to Jiuzhaigou valley, as serpentine appears frequently, it takes 10 hours (almost a whole day) on the way. The bus goes along Minjiang River Valley (one of the ancient tea horse route) to its source Mt.Gonggangling. I have to say the sightseeing there is gorgeous! Another choice is go by air, which is much more comfortable and safe. It is easy to take a 45min flight, and then 1 1/2 hour driving to arrive there. There are more than ten-scheduled flights every day in busy seasons. The altitude of Jiuhuang airport is about 3500m.
Aftter your visiting Jiuzhaigou, you can also take the bus back to Chengdu. If you want to make further tour in Tibet area, you can also change your bus at Zhuanzhusi or Songpan from where you take the bus to Huanglong or Hongyuan. Hongyuan is especially recommended by us because you can see the vast grassland there, and after that you can take the bus back to Chengdu via Miyaluo and Lixian county. By this route you can see more beautiful scenery.