What is the best way to reach Huangshan from Yangshuo?

The distance is about 808 miles (1,300 km). You may take a bus to Guilin Airport from Yangshuo Bus Station. Then, fly to Hefei (about 2 hours). Afterwards, take a bus to the Hefei Bus Station (about 1 hour), and transfer to a bus to the mountain (about 4 hours). :)

thank you for the answer! :) is there any chance to reach to the mountain by trains? :)

Oh, there are some mistakes about the answer above.
So I need to tell you that the bus to the mountain departs from Hefei East Bus Station (No. 517, East Changjiang Road). Not the Main Bus Station!!!
The buses are scheduled at 7:40, 8:00, 9:20, 10:40, 13:15, 13:43, and 14:40. The fare is CNY98.

In addition, upon landing at Hefei Airport, you may take shuttle bus line 1 to Chaohu Road Station. Then, take a taxi to East Bus Station for around CNY 12. :)

Yes, you may take a bus to Guilin Railway Station from Yangshuo Bus Station (about 70 minutes).
Then, take a bullet train to Hefei first (about 7.5 hours). There is only one departure at 9:56. Upon arrival, take bus line 11 to Hefei South Railway Station and take a bullet train to HS North Railway Station (about 1.5 hours).
Afterwards, you can find many direct shuttle buses that can take you to the scenic area.