It is suggested that you use the convenient MTR system. Staring from Causeway Bay, please take the Island Line and get off at Admiralty.

At Admiralty, please transfer to the Tsue Wan Line and then transfer to Kwun Tong Line at Prince Edwar. Finally, transfer to East Rail Line at Kowloon Tong which could lead you to Luohu.

Well, for brief: Causeway Bay-->Admiralty-->Prince Edward-->Kowloon Tong-->Luohu

The journey is about 65 minutes and costs 40.8HK$ per adult.

Hi Mr. Thilak, Mr. Shan has give one of the methods. Here is another one, please take the MTR to Admiralty and then to Tsim Sha Tsui. Then, you could walk to the East Tsim Sha Tsui of the East Rail Line in 5 minutes. These two stations are connected together that you don't have to exit the station. The rail here could drive to Luohu directly in 40 minutes.