Which is the best route to visit Badaling great wall of China from wangfujing area?

K.S, you can take subway line one from Wangfujing Station and get off at Tiananmen West Station, get out of Exit B and walk around 220 meters to find the bus station where you can take no. 5 bus to reach Deshengmen. There you can take no.877 bus to reach the wall.

Is there no any direct bus from Wangfujing area? Is it possible to take a taxi from Wangfujing area to the wall? How much it wll cost approximately?

There is no direct bus. If you plan to take a taxi, then the driver charges at least CNY 500 for a round trip. No drivers will take you there and return with empty seats.