Hi,Ms.Lu
The taxi fare from Beijing South Railway Station to Beijing World Trade Center is about 30RMB. Alternatively, you can take subway with a fare of CNY2. First take subway line 4 from Beijing South Railway Station to Xi Dan and then subway line 1 from Xi Dan to Guo Mao (International Trade Center). Good luck!

Thank you Ms.Fiona. Besides using Taxi, what are the cheap and easiest transportation to go to The Badaling Great Wall from Guo Mao(International Trade Center).How to go about it? Thanks

To Badaling: Take subway from Guomao Station to Tian'anmen West and get off from Exit B (the northeast exit). Then find the bus station nearby the exit. Take Bus 5 to Deshengmen. At the same station you can find Bus 919, the bus can take you direct to Badaling.