It costs 250RMB from Guangzhou to HK AIrport directly. BUs Available at China Marriott Guangzhou. It needs 3.5 hours. If you travel by train, you can take train at GUangzhou East Railway Station to Hung Hom Station of HK in Kowloon. It costs 190RMB for nearly 2 hours. Then take airport bus A21 to the airport: 33HKD for nearly one hour.