What is the distance between Guangzhou airport and Guiyang? Where to take long distance coach?

There is about 1120km between the two places, so it is suggested to take the trains.
From Guangzhou airport, you can take the airport shuttle bus line 1 to reach local Civial Aviation Ticket Office which is near the local railway station. Then you can go to the railway station to take the trains to reach GY. For the train's timetable, you can refer to https://www.travelchinaguide.com/china-trains/.
If you do not want to spend long time on the train, it is suggested to take a flight to reach GY from Guangzhou airport directly.