We are staying at JW Marriott Beijing, how can we go to the PEK airport?

Walk from your hotel to Dawang Road MTR Station to take subway line 1 to Guomao Station, from where you can walk to Dastrongeiyao (Guomao Bridge) to take shuttle bus line 1 to PEK directly.

Or upon arrival at Guomao MTR Station, you can transfer to subway line 10 to Sanyuanqiao, where you can transfer to Express Train to PEK.