which bus route service can i take from HKG airport to canton fair in guangzhou, what are the charge

There is no direct bus to reach the canton fair site, so you may need to transfer in Guangzhou.
From the airport, u can find the direct buses to reach Hotel Landmark Canton and then you can take a taxi to reach the canton fair site.
The bus fare for the hotel is 250HK$ per peron and the taxi fare is around 50RMB.