Most of these wholesale markets are located close to Guangzhou Railway Station and Guangzhou East Railway Station. From Guangzhou Airport, you could take shuttle bus Line 1 to Guangzhou Railway Station or Line6A to the east station. The east station could also be reached by subway Line 3 from the airport.
Ps: Baima Market is in walking-distance from Guangzhou Railway Station.

Thanks Jamie, How long it will take in hours and do you know how much is the fare? thanks

It takes about 45 minutes from the airport to Guangzhou Railway Station bu bus line 1, and the ticket price is CNY16. To Guangzhou east railway station, it takes 60 minutes by line 6A and costs CNY20, and takes about 30 minutes and costs CNY12.