I will be arriving to Capital Airport around midnight. My hotel is near West Railway Station.

According to your arrival time, you are advised to take shuttle bus Xidan Night Line and get off at Xidan Station first. The operating hours of this bus line are from 24:00 to the last domestic flight arrival. Thus you can catch it. The ticket fare is CNY 24 per person. After arriving, take a taxi to your hotel directly. The cab fare is CNY 30-40 at night.