There are three ways you can get to Hong Kong from Baiyun Airport, one is to take bus or taxi to Guangzhou East Railway Station and take direct train to Hung Hom. The other way is to take train to Shenzhen first, and then pass the customs and take MTR to downtown Hong Kong. The last way is to take direct bus to Hong Kong.
But since you'll arrive at late night, the earliest train from Guangzhou East to Hung Hom is at 08:19 in the morning, the earliest train from Guangzhou Railway Station to Shenzhen Railway Station is at 04:38 in the morning, the train arrive at 06:15 and the Luohu Customs open at 06:30.
If you go to Shenzhen first,take airport express Bus 1 to Guangzhou Railway Station and then wait there for the first train.
The earliest bus leave at 05:15 in the morning at Hotel Landmark Canton. This hotel can be reached by taxi.
The cheapest is to take train to Shenzhen and then pass the customs, the fastest is to take Bus, it costs around HKD90 to reach Mong Kok.

Except of hiring a cab driving to the Huanggang Port of Shenzhen, I'm afraid there is no public transport in operation at late night.

So, after arrive at the airport, please go to take the airport shuttle bus Line 6A to Guangzhou East Railway Station. Stay one-night at a nearby hotel or the waiting hall of the railway station, and then take the first train at 06:20 to Shenzhen Railway Station at Luohu. Go through the Luohu border, you could enter into Hong Kong.

Hi,
is there also a bus which drives after 1 am?
Thanks

There is no bus drives after 1 am.

At which time drives the last one?
And then I would have to hire a taxi?

Hi Martin, the airport shuttle bus will be in operation until the last flight arrival. However, there will be no bus or train to Shenzhen after 23:00.

Hi,
I wanted stay the night in an Hotel and take then a train.
But if there is no bus available I would have to stay in an Hotel near the airport and get the next day to Guangzhou but if there is the chance to take the bus I could choose an Hotel near the trainstation.
So is there a bus 6a or not?

Hi martin.Dont worry.if there is flight arrival there is bus.you can take a bus line one to railwaystation...have a nice trip...