is there a long distance bus transportation from guilin to zhangjiajie? Can I buy it online?

Well, there is bus running between. You can take the long-distance bus at the local bus station to Zhangjiajie directly. But as I know, only one bus runs for the journey every day, departing at 19:00.
As I know, the bus ticket can only be bought at the local bus station.

July Thanks!! Do you know how many hours it takes the trip?
Also, I will be in Zhangjiajie 2 days (from the morning that I get there until the next day at night, that I will take a flight to Shangai). In these two days, what places do you recomend me to go? Thanks!

Hello! I am staying in Zhangjiajie for 5 days. Do you think it will be any seat available if I buy the ticket as soon as I arrive the city? As I read in this post I cannot buy it in advance. Thanks!

Yeah, I heard it's true.