How to get there from beijing wangfujing area to National stadium ? Thank you very much !

You can take a taxi to the destination directly. The cab fare is CNY 30 to 35.
If by subways, you need to take subway line 5 at Dengshikou Station, and get off at Huixinxijie Nankou Station. Then transfer to subway line 10 to Beitucheng Station and take subway line 8 to Olympic Sports Center Station. After arriving, walk to the destination directly. The fare is CNY 4 per adult. And it will take around 22 mins on the way.
You can choose the way you like. :-)