Which is the best shuttle bus to get from PEK to Pentahotel in Dongcheng District?

Take shuttle bus line 7 from PEK to Ciqikou Station. Then, walk north along Chongwenmenwai Street for about 600 yards to it.

Or, you can take Airport Express from PEK to Dongzhimen Station. Then, change to metro line 2 to Chongwenmen Station, Exit D2, and you can see it. .:)