I'll be visiting Chengdu-Jiuzhaigou-Lijiang in Oct. Is there a bus service from Jiuzhaigou to Lijiang?

I am afraid that there is no such bus.

Hi, Ooi.
I am afraid that there is no direct bus between the two places.
But there are several other methods transported between the two places.
If you want the fastest one, you can fly from Jiuzhaigou to Chengdu and from fly from Chengdu to Lijiang. It is fast, but more expensive if you cannot book the discount tickets.
Or you can choose the economical way, you can take a bus from Jiuzhaigou to Chengdu. From Chengdu, you can take a train for Kunming. From Kunming, you can also take trains for LJ.
Hope the information can help you.