You can take the Subway Island Line from the Causeway Bay Station, get off at the Admiralty Station and change to the Tswen Wan Line, get off at the Tsim Sha Tsui Station and go to the Tsim Sha Tsui East Station,take the East Railway Line to the Lo Wu Station.After passing the customs, you can take the Airport Bus Line 1/2 near the Shenzhen Railway Station (It is close to the port), the final station is the airport.